docs: def from_json(cls, key, scopes, subject=None):
          """Alternate constructor intended for using JSON format of private key.
  
          Args:
              key (dict) - Parsed JSON with service account credentials.
              scopes (Union[str, collections.Iterable[str]]) -
                  List of permissions that the application requests.
              subject (str) - The email address of the user for which
                  the application is requesting delegated access.
  
          Returns:
              ServiceAccount
          """
          credentials_type = key['type']
          if credentials_type != 'service_account':
              raise ValueError('key: expected type service_account '
                               '(got %s)' % credentials_type)
          email = key['client_email']
          key = OpenSSL.crypto.load_privatekey(OpenSSL.crypto.FILETYPE_PEM,
                                               key['private_key'])
  
          return cls(key=key, email=email, scopes=scopes, subject=subject)