code: func (c *Client) SupportedModules() (map[string]string, error) {
  	var result map[string]string
  	ctx, cancel := context.WithTimeout(context.Background(), subscribeTimeout)
  	defer cancel()
  	err := c.CallContext(ctx, &result, "rpc_modules")
  	return result, err
  }
docs: // SupportedModules calls the rpc_modules method, retrieving the list of
  // APIs that are available on the server.