docs: Add class docstrings for LizardExtension in complexity-related modules

This commit introduces detailed docstrings for the LizardExtension classes in lizardcomplextags.py, lizardmccabe.py, and lizardmodified.py. The docstrings clarify the purpose and functionality of each extension, enhancing code documentation and maintainability.

Author: terryyin

lizard_ext/lizardcomplextags.py

@@ -5,10 +5,16 @@
 
 
 class LizardExtension(object):  # pylint: disable=R0903
+    """
+    Complex tags extension: records all complexity-adding keywords and their line numbers.
+    Uses reader.conditions (combined set of all condition types) to track all
+    complexity contributors: control flow, logical operators, case labels, and ternary.
+    """
 
     # pylint: disable=W0221
     def __call__(self, tokens, reader):
         context = reader.context
+        # Use combined conditions set - intentionally includes all types
         conditions = reader.conditions
         for token in tokens:
             yield token

lizard_ext/lizardmccabe.py

@@ -14,9 +14,14 @@
 
 
 class LizardExtension(ExtensionBase):  # pylint: disable=R0903
+    """
+    McCabe extension: only counts the first 'case' in a switch statement.
+    Consecutive cases without code between them don't add to complexity.
+    Works by detecting case tokens (conceptually from reader.case_keywords).
+    """
 
     def _state_global(self, token):
-        if token == "case":
+        if token == "case":  # Detect case keywords
             self._state = self._in_case
 
     def _in_case(self, token):

lizard_ext/lizardmodified.py

@@ -6,14 +6,19 @@
 
 
 class LizardExtension(object):  # pylint: disable=R0903
+    """
+    Modified CCN extension: counts entire switch/case as 1 complexity.
+    Adds +1 for 'switch', subtracts -1 for each 'case'.
+    Works with switch/case keywords (conceptually from reader.case_keywords).
+    """
 
     def __call__(self, tokens, reader):
         for token in tokens:
-            if token == 'switch':
+            if token == 'switch':  # Add complexity for switch statement
                 reader.context.add_condition()
                 if hasattr(reader.context, "add_nd_condition"):
                     reader.context.add_nd_condition()
-            elif token == 'case':
+            elif token == 'case':  # Subtract complexity for each case
                 reader.context.add_condition(-1)
                 if hasattr(reader.context, "add_nd_condition"):
                     reader.context.add_nd_condition(-1)