def get_units(self, loss_types):
        """
        :param: a list of loss types
        :returns: an array of units as byte strings, suitable for HDF5
        """
        lst = []
        for lt in loss_types:
            if lt.endswith('_ins'):
                lt = lt[:-4]
            if lt == 'occupants':
                unit = 'people'
            else:
                unit = self.units[lt]
            lst.append(encode(unit))
        return numpy.array(lst)