Set an unique input type.

        If you use this then you have only one input for the play.

def set_input_type(self, type_or_parse):
        """ Set an unique input type.

        If you use this then you have only one input for the play.
        """
        self._inputs = OrderedDict()
        default_inputs = self.engine.in_name
        if len(default_inputs) > 1:
            raise ValueError("Need more than one input, you sould use `add_input` for each of them")
        self.add_input(default_inputs[0], type_or_parse)