def imt_periods(self):
        """
        :returns: the IMTs with a period, as objects
        """
        imts = []
        for im in self.imtls:
            imt = from_string(im)
            if hasattr(imt, 'period'):
                imts.append(imt)
        return imts
def imt_periods ( self ) : imts = [ ] for im in self . imtls : imt = from_string ( im ) if hasattr ( imt , 'period' ) : imts . append ( imt ) return imts
:returns: the IMTs with a period, as objects