code: def __security_definitions_descriptor(self, issuers):
      
      if not issuers:
        result = {
            _DEFAULT_SECURITY_DEFINITION: {
                'authorizationUrl': '',
                'flow': 'implicit',
                'type': 'oauth2',
                'x-google-issuer': 'https://accounts.google.com',
                'x-google-jwks_uri': 'https://www.googleapis.com/oauth2/v3/certs',
            }
        }
        return result
  
      result = {}
  
      for issuer_key, issuer_value in issuers.items():
        result[issuer_key] = {
            'authorizationUrl': '',
            'flow': 'implicit',
            'type': 'oauth2',
            'x-google-issuer': issuer_value.issuer,
        }
  
        # If jwks_uri is omitted, the auth library will use OpenID discovery
        # to find it. Otherwise, include it in the descriptor explicitly.
        if issuer_value.jwks_uri:
          result[issuer_key]['x-google-jwks_uri'] = issuer_value.jwks_uri
  
      return result
docs: Create a descriptor for the security definitions.
  
      Args:
        issuers: dict, mapping issuer names to Issuer tuples
  
      Returns:
        The dict representing the security definitions descriptor.