code: func (d *DialParams) CheckAndSetDefaults() error {
  	if d.From == nil {
  		return trace.BadParameter("parameter From required")
  	}
  	if d.To == nil {
  		return trace.BadParameter("parameter To required")
  	}
  
  	return nil
  }
docs: // CheckAndSetDefaults makes sure the minimal parameters are set.