diff --git a/pyproject.toml b/pyproject.toml
index f32c54c..187ad05 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -146,8 +146,7 @@ no_site_packages = false
 
 # Untyped definitions and calls
 # https://mypy.readthedocs.io/en/stable/config_file.html#untyped-definitions-and-calls
-# TODO: enable and fix errors
-check_untyped_defs = false
+check_untyped_defs = true
 
 # Miscellaneous strictness flags
 # https://mypy.readthedocs.io/en/latest/config_file.html#miscellaneous-strictness-flags
@@ -170,7 +169,7 @@ show_absolute_path = false
 
 # None and Optional handling
 # https://mypy.readthedocs.io/en/latest/config_file.html#none-and-optional-handling
-strict_optional = false
+strict_optional = true
 
 # Miscellaneous
 # https://mypy.readthedocs.io/en/latest/config_file.html#miscellaneous
diff --git a/src/aibs_informatics_core/collections.py b/src/aibs_informatics_core/collections.py
index 4cf5474..5c1599c 100644
--- a/src/aibs_informatics_core/collections.py
+++ b/src/aibs_informatics_core/collections.py
@@ -268,7 +268,7 @@ def __post_init__(self, *args, **kwargs):
         """Default __post_init__ method. Safe parent __post_init__ method calls"""
 
         try:
-            post_init = super().__post_init__  # type: ignore[attr]
+            post_init = super().__post_init__  # type: ignore[misc]
         except AttributeError:
             pass
         else:
diff --git a/src/aibs_informatics_core/env.py b/src/aibs_informatics_core/env.py
index 110cfee..3f6cee1 100644
--- a/src/aibs_informatics_core/env.py
+++ b/src/aibs_informatics_core/env.py
@@ -180,7 +180,7 @@ def load_env_type__from_env(cls) -> EnvType:
         return EnvType(env_type)
 
     @classmethod
-    def load_env_label__from_env(cls) -> str:
+    def load_env_label__from_env(cls) -> Optional[str]:
         return get_env_var(ENV_LABEL_KEY, ENV_LABEL_KEY_ALIAS, LABEL_KEY, LABEL_KEY_ALIAS)
 
 
@@ -197,7 +197,7 @@ def env_base(self) -> EnvBase:
         try:
             return self._env_base
         except AttributeError:
-            self.env_base = None
+            self.env_base = None  # type: ignore[assignment]
             return self._env_base
 
     @env_base.setter
@@ -213,8 +213,8 @@ def env_base(self, env_base: Optional[EnvBase] = None):
 
 
 class EnvBaseEnumMixins:
-    def prefix_with(self, env_base: EnvBase = None) -> str:
-        env_base = get_env_base(env_base)
+    def prefix_with(self, env_base: Optional[EnvBase] = None) -> str:
+        env_base: EnvBase = get_env_base(env_base)
         if isinstance(self, Enum):
             return env_base.prefixed(self.value)
         else:
diff --git a/src/aibs_informatics_core/executors/base.py b/src/aibs_informatics_core/executors/base.py
index 6250a38..907528a 100644
--- a/src/aibs_informatics_core/executors/base.py
+++ b/src/aibs_informatics_core/executors/base.py
@@ -187,7 +187,7 @@ def write_output__file(cls, output: JSON, local_path: Path) -> None:
         """
 
         if local_path.is_dir() or (
-            local_path.parent.exists and not os.access(local_path.parent, os.W_OK)
+            local_path.parent.exists() and not os.access(local_path.parent, os.W_OK)
         ):
             raise ValueError(
                 f"local path specified {local_path} cannot be written to. " f"Must be a file "
diff --git a/src/aibs_informatics_core/models/api/http_parameters.py b/src/aibs_informatics_core/models/api/http_parameters.py
index 8884b9b..ee4647a 100644
--- a/src/aibs_informatics_core/models/api/http_parameters.py
+++ b/src/aibs_informatics_core/models/api/http_parameters.py
@@ -52,10 +52,14 @@ def merged_params(self) -> Dict[str, JSON]:
         return request_json
 
     @classmethod
-    def from_stringified_route_params(cls, parameters: Dict[str, str]) -> Dict[str, JSON]:
+    def from_stringified_route_params(
+        cls, parameters: Optional[Dict[str, str]]
+    ) -> Dict[str, JSON]:
         evaluated_params = dict()
+
+        input_params = parameters or dict()
         # literal_eval as much as we can to python primitives, our schema will take care of rest.
-        for k, v in parameters.items():
+        for k, v in input_params.items():
             try:
                 evaluated_params[k] = ast.literal_eval(urllib.parse.unquote(v))
             except Exception:
@@ -94,7 +98,7 @@ def to_stringified_query_params(cls, parameters: Optional[Dict[str, JSON]]) -> D
         return {QUERY_PARAMS_KEY: urlsafe_b64encode(parameters_str.encode()).decode()}
 
     @classmethod
-    def to_stringified_request_body(cls, parameters: Optional[Dict[str, JSON]]) -> str:
+    def to_stringified_request_body(cls, parameters: Optional[Dict[str, JSON]]) -> Optional[str]:
         if parameters is None or len(parameters) == 0:
             return None
         return json.dumps(parameters, sort_keys=True)
diff --git a/src/aibs_informatics_core/models/base/model.py b/src/aibs_informatics_core/models/base/model.py
index 360a1be..058c80e 100644
--- a/src/aibs_informatics_core/models/base/model.py
+++ b/src/aibs_informatics_core/models/base/model.py
@@ -88,9 +88,6 @@ def from_path(cls: Type[T], path: Path, **kwargs) -> T:
     def to_path(self, path: Path, **kwargs):
         ...  # pragma: no cover
 
-    def copy(self: T, **kwargs) -> T:
-        ...  # pragma: no cover
-
 
 # --------------------------------------------------------------
 #                             BaseModel ABC
@@ -130,9 +127,6 @@ def from_path(cls: Type[M], path: Path, **kwargs) -> M:
     def to_path(self, path: Path, **kwargs):
         path.write_text(self.to_json(**kwargs))
 
-    def copy(self: M, **kwargs) -> M:
-        return self.from_dict(self.to_dict(**kwargs), **kwargs)
-
 
 # --------------------------------------------------------------
 #                        DataClassModel
diff --git a/src/aibs_informatics_core/models/db/base.py b/src/aibs_informatics_core/models/db/base.py
index 5072eb8..d7e9825 100644
--- a/src/aibs_informatics_core/models/db/base.py
+++ b/src/aibs_informatics_core/models/db/base.py
@@ -107,7 +107,13 @@ def __new__(cls, *values):
         obj._sort_key_name = values[2]
         obj._index_name = values[3]
         obj._attributes = values[4] if len(values) > 4 else None
-        obj._all_values = tuple(values)
+        obj._all_values = (
+            obj._value_,
+            obj._key_name,
+            obj._sort_key_name,
+            obj._index_name,
+            obj._attributes,
+        )
         return obj
 
     @classmethod
diff --git a/src/aibs_informatics_core/models/demand_execution/param_pair.py b/src/aibs_informatics_core/models/demand_execution/param_pair.py
index 47e43ca..dd01a79 100644
--- a/src/aibs_informatics_core/models/demand_execution/param_pair.py
+++ b/src/aibs_informatics_core/models/demand_execution/param_pair.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 from dataclasses import dataclass, field
-from typing import Dict, FrozenSet, Iterable, List, Optional
+from typing import Dict, FrozenSet, Iterable, List, Optional, Union
 
 from aibs_informatics_core.models.aws.s3 import S3URI
 from aibs_informatics_core.models.base import (
@@ -105,7 +105,7 @@ def from_pairs(cls, *pairs: ParamPair) -> List[ParamSetPair]:
             List[ParamSetPair]: A list of ParamSetPairs
         """
         # group pairs only by outputs
-        output_set_pairs: Dict[str, ParamSetPair] = {}
+        output_set_pairs: Dict[Union[str, None], ParamSetPair] = {}
         for pair in pairs:
             if pair.output not in output_set_pairs:
                 output_set_pairs[pair.output] = ParamSetPair(
@@ -210,7 +210,7 @@ def from_pairs(cls, *pairs: JobParamPair) -> List[JobParamSetPair]:
             List[JobParamSetPair]: A list of JobParamSetPairs
         """
         # group pairs only by outputs
-        output_set_pairs: Dict[ResolvableJobParam, JobParamSetPair] = {}
+        output_set_pairs: Dict[Union[ResolvableJobParam, None], JobParamSetPair] = {}
         for pair in pairs:
             if pair.output not in output_set_pairs:
                 output_set_pairs[pair.output] = JobParamSetPair(
diff --git a/src/aibs_informatics_core/models/demand_execution/parameters.py b/src/aibs_informatics_core/models/demand_execution/parameters.py
index 340967f..ab346f7 100644
--- a/src/aibs_informatics_core/models/demand_execution/parameters.py
+++ b/src/aibs_informatics_core/models/demand_execution/parameters.py
@@ -147,11 +147,12 @@ def _validate_param_pairs(self):
 
         # Validate no duplicate output sets
         seen = set()
-        duplicate_output_sets = [
-            s.outputs
-            for s in self.param_set_pairs
-            if s.outputs in seen or (s.outputs and seen.add(s.outputs))
-        ]
+        duplicate_output_sets = []
+        for s in self.param_set_pairs:
+            if s.outputs in seen:
+                duplicate_output_sets.append(s.outputs)
+            if s.outputs:
+                seen.add(s.outputs)
         if len(duplicate_output_sets) > 0:
             raise ValidationError(
                 "Duplicate output set(s) in input_output_map: " f"{duplicate_output_sets}"
@@ -234,7 +235,7 @@ def param_set_pairs(self) -> List[ParamSetPair]:
         param_set_pairs: List[ParamSetPair] = []
         param_pairs: List[ParamPair] = []
         if self.param_pair_overrides:
-            seen_outputs: Set[str] = set()
+            seen_outputs: Set[Union[str, None]] = set()
             for pair in self.param_pair_overrides:
                 if isinstance(pair, ParamSetPair):
                     seen_outputs.update(pair.outputs)
diff --git a/src/aibs_informatics_core/utils/decorators.py b/src/aibs_informatics_core/utils/decorators.py
index e5e51ca..fe042c6 100644
--- a/src/aibs_informatics_core/utils/decorators.py
+++ b/src/aibs_informatics_core/utils/decorators.py
@@ -71,6 +71,7 @@ def f_retry(*args, **kwargs):
                         [callback(ex) for callback in applicable_callbacks]
                     ):
                         raise ex
+                    assert logger is not None
                     logger.warning("%s, Retrying in %d seconds..." % (str(ex), mdelay))
                     time.sleep(mdelay)
                     mtries -= 1
diff --git a/src/aibs_informatics_core/utils/os_operations.py b/src/aibs_informatics_core/utils/os_operations.py
index e5b29d3..b873292 100644
--- a/src/aibs_informatics_core/utils/os_operations.py
+++ b/src/aibs_informatics_core/utils/os_operations.py
@@ -406,8 +406,8 @@ def env_var_overrides(*env_vars: EnvVarItemType):
     try:
         yield
     finally:
-        for key, value in original_env_vars.items():
-            if value is None:
-                del os.environ[key]
+        for k, v in original_env_vars.items():
+            if v is None:
+                del os.environ[k]
             else:
-                os.environ[key] = value
+                os.environ[k] = v
diff --git a/test/aibs_informatics_core/models/base/test_model.py b/test/aibs_informatics_core/models/base/test_model.py
index 93ce167..eb471d7 100644
--- a/test/aibs_informatics_core/models/base/test_model.py
+++ b/test/aibs_informatics_core/models/base/test_model.py
@@ -68,14 +68,6 @@ def test__BaseModel__to_json__from_json():
     assert new_model.a_str == "I'm a string!"
 
 
-def test__BaseModel__copy():
-    model = SimpleBaseModel(a_str="I'm a string!", a_int=42)
-    new_model = model.copy()
-    assert new_model.a_int == 42
-    assert new_model.a_str == "I'm a string!"
-    assert new_model is not model
-
-
 # ----------------------------------------------------------
 #                       DataClassModel tests
 # ----------------------------------------------------------