/// <summary>
/// Invokes a duplex streaming call asynchronously.
/// In duplex streaming scenario, client sends a stream of requests and server responds with a stream of responses.
/// The response stream is completely independent and both side can be sending messages at the same time.
/// </summary>
public abstract AsyncDuplexStreamingCall <TRequest, TResponse> AsyncDuplexStreamingCall <TRequest, TResponse>(Method <TRequest, TResponse> method, string?host, CallOptions options)
where TRequest : class
where TResponse : class;
/// <summary>
/// Invokes a simple remote call asynchronously.
/// </summary>
public abstract AsyncUnaryCall <TResponse> AsyncUnaryCall <TRequest, TResponse>(Method <TRequest, TResponse> method, string?host, CallOptions options, TRequest request)
where TRequest : class
where TResponse : class;