/// <summary>
 /// Deletes a repository invitation.
 /// </summary>
 /// <remarks>
 /// See the <a href="https://developer.github.com/v3/repos/invitations/#delete-a-repository-invitation">API documentation</a> for more information.
 /// </remarks>
 /// <param name="repositoryId">The id of the repository.</param>
 /// <param name="invitationId">The id of the invitation.</param>
 public IObservable <bool> Delete(long repositoryId, int invitationId)
 {
     return(_client.Delete(repositoryId, invitationId).ToObservable());
 }