code: func (c *helpCacher) rpcMethodHelp(method string) (string, error) {
  	c.Lock()
  	defer c.Unlock()
  
  	// Return the cached method help if it exists.
  	if help, exists := c.methodHelp[method]; exists {
  		return help, nil
  	}
  
  	// Look up the result types for the method.
  	resultTypes, ok := rpcResultTypes[method]
  	if !ok {
  		return "", errors.New("no result types specified for method " +
  			method)
  	}
  
  	// Generate, cache, and return the help.
  	help, err := btcjson.GenerateHelp(method, helpDescsEnUS, resultTypes...)
  	if err != nil {
  		return "", err
  	}
  	c.methodHelp[method] = help
  	return help, nil
  }
docs: // rpcMethodHelp returns an RPC help string for the provided method.
  //
  // This function is safe for concurrent access.