@staticmethod
def _add_out_reqs(output_request):
    """Add additional output requests as needed.

        Parameters
        ----------
        output_request : list
            Output variables requested from SAM.

        Returns
        -------
        output_request : list
            Output variable list with cf_mean and resource mean out vars.
        """
    if 'cf_mean' not in output_request:
        output_request.append('cf_mean')
    return output_request
