code: def _validate_class_definition(meta, classname, bases, dict_):
          
          # let the BaseMatcher class be created without hassle
          if meta._is_base_matcher_class_definition(classname, dict_):
              return
  
          # ensure that no important magic methods are being overridden
          for name, member in dict_.items():
              if not (name.startswith('__') and name.endswith('__')):
                  continue
  
              # check if it's not a whitelisted magic method name
              name = name[2:-2]
              if not name:
                  continue  # unlikely case of a ``____`` function
              if name not in meta._list_magic_methods(BaseMatcher):
                  continue
              if name in meta.USER_OVERRIDABLE_MAGIC_METHODS:
                  continue
  
              # non-function attributes, like __slots__, are harmless
              if not inspect.isfunction(member):
                  continue
  
              # classes in this very module are exempt, since they define
              # the very behavior of matchers we want to protect
              if member.__module__ == __name__:
                  continue
  
              raise RuntimeError(
                  "matcher class %s cannot override the __%s__ method" % (
                      classname, name))
docs: Ensure the matcher class definition is acceptable.
          :raise RuntimeError: If there is a problem