code: func (c *Client) ReleaseRollback(appIdentity, release, message string) (*Release, error) {
  	params := struct {
  		Release string `json:"release"`
  	}{
  		Release: release,
  	}
  	rh := RequestHeaders{CommitMessage: message}
  	var releaseRes Release
  	return &releaseRes, c.PostWithHeaders(&releaseRes, "/apps/"+appIdentity+"/releases", params, rh.Headers())
  }
docs: // Rollback to an existing release.
  //
  // appIdentity is the unique identifier of the Release's App. release is the
  // unique identifier of release.