docs: def call (self, to, **options):
          """
          Places a call or sends an an IM, Twitter, or SMS message. To start a call, use the Session API to tell Tropo to launch your code.
          Arguments: to is a String.
          Argument: **options is a set of optional keyword arguments.
          See https://www.tropo.com/docs/webapi/call
          """
          self._steps.append(Call (to, **options).obj)