docs: def _get_call_class(method):
      """Find the call class for method if it exists else create one."""
      call_base, call_name = method.split('.', 1)
      # import the call class's module
      mod = __import__('ubersmith.calls.{0}'.format(call_base), fromlist=[''])
      # grab all the public members of the module
      gen = (getattr(mod, x) for x in dir(mod) if not x.startswith('_'))
      # filter them down to subclasses of BaseCall
      gen = (x for x in gen if type(x) is type and issubclass(x, BaseCall))
      # return first one that matches our method
      for call_class in gen:
          if call_class.method == method:
              return call_class
      else:
          class GenericCall(BaseCall):
              method = '.'.join((call_base, call_name))
          return GenericCall