code: def AddFileDescriptor(self, file_desc):
      
  
      self._AddFileDescriptor(file_desc)
      # TODO(jieluo): This is a temporary solution for FieldDescriptor.file.
      # Remove it when FieldDescriptor.file is added in code gen.
      for extension in file_desc.extensions_by_name.values():
        self._file_desc_by_toplevel_extension[
            extension.full_name] = file_desc
docs: Adds a FileDescriptor to the pool, non-recursively.
  
      If the FileDescriptor contains messages or enums, the caller must explicitly
      register them.
  
      Args:
        file_desc: A FileDescriptor.