text: # Copyright 2020 The Vertizee Authors
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Utilities supporting abstract base classes."""
  
  from typing import Type, TypeVar
  
  T = TypeVar("T")
  
  
  def check_methods(C: Type[T], *methods: str) -> bool:
      """Function to check if methods are members of a class."""
      mro = C.__mro__
      for method in methods:
          for B in mro:
              if method in B.__dict__:
                  if B.__dict__[method] is None:
                      return NotImplemented
                  break
          else:
              return NotImplemented
      return True
  