code: function getCall(channel, path, options) {
    var deadline;
    var host;
    var parent;
    var propagate_flags;
    var credentials;
    if (options) {
      deadline = options.deadline;
      host = options.host;
      parent = options.parent ? options.parent.call : undefined;
      propagate_flags = options.propagate_flags;
      credentials = options.credentials;
    }
    if (deadline === undefined) {
      deadline = Infinity;
    }
    var call = channel.createCall(path, deadline, host,
                                  parent, propagate_flags);
    if (credentials) {
      call.setCredentials(credentials);
    }
    return call;
  }
docs: Get a call object built with the provided options.
  @param {grpc.Channel} channel
  @param {string} path
  @param {grpc.Client~CallOptions=} options Options object.