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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def output_reference(self, name):
 """Return a reference to the given output for use in an input of a next Step. For a Step named `echo` that has an output called `echoed`, the reference `echo/echoed` is returned. Args: name (str):
 the name of the Step output Raises: ValueError: The name provided is not a valid output name for this Step. """

        if name not in self.output_names:
            raise ValueError('Invalid output "{}"'.format(name))
        return Reference(step_name=self.name_in_workflow, output_name=name)