set input parameters for elegant tracking, available keys: 'ltefile', 'elefile'

def _setElegant(self, **infiles):
        """ set input parameters for elegant tracking, available keys: 'ltefile', 'elefile'
        """
        ltefile, elefile = infiles['ltefile'], infiles['elefile']
        self.lattice_file = ltefile
        self.elegant_file = elefile