code: func (fb *Firebase) String() string {
  	path := fb.url + "/.json"
  
  	fb.paramsMtx.RLock()
  	if len(fb.params) > 0 {
  		path += "?" + fb.params.Encode()
  	}
  	fb.paramsMtx.RUnlock()
  	return path
  }
docs: // String returns the string representation of the
  // Firebase reference.