def exists(self, file_ref):
        """
        Parameters
        ----------
        file_ref: str
            reference of file.
            Available references:  'idf', 'epw', 'eio', 'eso', 'mtr', 'mtd', 'mdd', 'err', 'summary_table'
            See EnergyPlus documentation for more information.

        Returns
        -------
        Boolean
        """
        if file_ref not in FILE_REFS:
            raise ValueError("Unknown file_ref: '%s'. Available: '%s'." % (file_ref, list(sorted(FILE_REFS._fields))))
        return os.path.isfile(self._path(file_ref))
Parameters
        ----------
        file_ref: str
            reference of file.
            Available references:  'idf', 'epw', 'eio', 'eso', 'mtr', 'mtd', 'mdd', 'err', 'summary_table'
            See EnergyPlus documentation for more information.

        Returns
        -------
        Boolean