fix: explicit is better than implicit

juju/application.py

@@ -659,27 +659,27 @@ async def set_constraints(self, constraints):
 
     async def refresh(
             self,
-            channel=None,
-            force=False,
-            force_series=False,
-            force_units=False,
+            channel: Optional[str] = None,
+            force: bool = False,
+            force_series: bool = False,
+            force_units: bool = False,
             path: Optional[Union[Path, str]] = None,
-            resources=None,
-            revision=None,
+            resources: Optional[Dict[str, str]] = None,
+            revision: Optional[int] = None,
             switch: Optional[str] = None,
         ):
         """Refresh the charm for this application.
 
-        :param str channel: Channel to use when getting the charm from the
+        :param str|None channel: Channel to use when getting the charm from the
             charm store, e.g. 'development'
         :param bool force_series: Refresh even if series of deployed
             application is not supported by the new charm
         :param bool force_units: Refresh all units immediately, even if in
             error state
-        :param Path|str path: Refresh to a charm located at path
-        :param dict resources: Dictionary of resource name/filepath pairs
-        :param int revision: Explicit refresh revision
-        :param str switch: Crossgrade charm url
+        :param Path|str|None path: Refresh to a charm located at path
+        :param dict[str,str]|None resources: Dictionary of resource name/filepath pairs
+        :param int|None revision: Explicit refresh revision
+        :param str|None switch: URL of a different charm to cross-grade to
 
         """
         if switch is not None and path is not None:
@@ -931,14 +931,17 @@ async def get_metrics(self):
         return await self.model.get_metrics(self.tag)
 
 
-def _refresh_origin(current_origin: client.CharmOrigin, channel=None, revision=None) -> client.CharmOrigin:
-    if channel is not None:
-        channel = Channel.parse(channel).normalize()
+def _refresh_origin(
+        current_origin: client.CharmOrigin,
+        channel: Optional[str] = None,
+        revision: Optional[int] = None,
+    ) -> client.CharmOrigin:
+    chan = None if channel is None else Channel.parse(channel).normalize()
 
     return client.CharmOrigin(
         source=current_origin.source,
-        track=channel.track if channel else current_origin.track,
-        risk=channel.risk if channel else current_origin.risk,
+        track=chan.track if chan else current_origin.track,
+        risk=chan.risk if chan else current_origin.risk,
         revision=revision if revision is not None else current_origin.revision,
         base=current_origin.base,
         architecture=current_origin.get('architecture', DEFAULT_ARCHITECTURE),

juju/model.py

@@ -2013,8 +2013,8 @@ async def add_local_resources(self, application, entity_url, metadata, resources
         :param str application: the name of the application
         :param client.CharmURL entity_url: url for the charm that we add resources for
         :param [string]string metadata: metadata for the charm that we add resources for
-        :param [string] resources: the paths for the local files (or oci-images) to be added as
-        local resources
+        :param dict[str, str] resources: the paths for the local files (or oci-images) to
+        be added as local resources
 
         :returns [string]string resource_map that is a map of resources to their assigned
         pendingIDs.

juju/origin.py

@@ -69,7 +69,7 @@ def __init__(self, track=None, risk=None):
         self.risk = risk
 
     @staticmethod
-    def parse(s):
+    def parse(s: str):
         """parse a channel from a given string.
         Parse does not take into account branches.