def get(self, id, pk='id', deleted=False):
        try:
            if pk == 'id':
                id = int(id)
            if deleted:
                spec = {pk: id}
            else:
                spec = {pk: id, 'data': {'$exists': 1}}
            fields = {'_id': 0}
            row = self.db.docs.find_one(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return Document(**row)
        raise NotFoundError('%s %s not found' % (pk, id))
def demag(isa, ax=0):
    """plot demag of NC/I7/ISA7 model
    Args:
      isa: Isa7/NC object
    """
    emag = [e for e in isa.elements if e.is_magnet()]
    demag = np.array([e.demagnetization(isa.MAGN_TEMPERATURE) for e in emag])
    _contour(ax, f'Demagnetization at {isa.MAGN_TEMPERATURE} °C',
             emag, demag, '-H / kA/m', isa)
    logger.info("Max demagnetization %f", np.max(demag))