new_contents: class Field:
      def __init__(self, name, return_type, description=None, arg_types=None, deprecation_reason=None):
          self.name = name
          self.return_type = return_type
          self.description = description
          self.arg_types = arg_types
          self.deprecation_reason = deprecation_reason
          self.is_deprecated = bool(deprecation_reason)
  
subject: Implement Field object