Fix pylint warnings

shell.py

@@ -47,7 +47,8 @@ def str_to_bool(string):
     return False
 
 
-def bytes_to_list_str(byte_data):
+def bytes_to_list_str(byte_data) -> str:
+    """Converts an iterable containing bytes to a string representation, using a list format"""
     size = len(byte_data)
     if BYTE_DATA_MAX_LEN:
         byte_data = byte_data[0:BYTE_DATA_MAX_LEN]
@@ -57,7 +58,11 @@ def bytes_to_list_str(byte_data):
     res += "]"
     return res
 
-def bytes_to_hexdump_str(byte_data):
+def bytes_to_hexdump_str(byte_data) -> str:
+    """
+    Converts an iterable containing bytes to a string representation
+    using a hexadecimal dump format
+    """
     offset = 0
     size = len(byte_data)
     if BYTE_DATA_MAX_LEN != 0 and BYTE_DATA_MAX_LEN < size:
@@ -154,6 +159,7 @@ def get_common_info_str(metric):
         res = res + "\n\tproperties: None"
     return res
 
+
 def get_metric_str(metric) -> str:
     """Return a string describing metric if it is known to Device"""
     value_str: str = get_typed_value_str(metric.datatype, metric)
@@ -163,7 +169,7 @@ def get_metric_str(metric) -> str:
 
 @cmd2.with_default_category('Enki')
 class SPShell(cmd2.Cmd):
-    # pylint: disable=too-many-instance-attributes, too-many-public-methods
+    # pylint: disable=too-many-instance-attributes, too-many-public-methods, global-statement
     """Enki Shell Interface"""
 
     def __init__(self, mqtt_if: MQTTInterface):
@@ -178,7 +184,8 @@ def __init__(self, mqtt_if: MQTTInterface):
         )
         self.byte_data_max_len = BYTE_DATA_MAX_LEN
         self.add_settable(
-            cmd2.Settable("byte_data_max_len", int, "Maximum number of bytes to display for byte data",
+            cmd2.Settable("byte_data_max_len", int,
+                          "Maximum number of bytes to display for byte data",
                           self, onchange_cb=self._on_change_byte_data_max_len)
         )