def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def spel(isa, with_axis=False, ax=0):
    """plot super elements of I7/ISA7 model
    Args:
      isa: Isa7 object
    """
    from matplotlib.patches import Polygon
    if ax == 0:
        ax = plt.gca()
    ax.set_aspect('equal')
    for se in isa.superelements:
        ax.add_patch(Polygon([n.xy
                              for nc in se.nodechains
                              for n in nc.nodes],
                             color=isa.color[se.color], lw=0))

    ax.autoscale(enable=True)
    if not with_axis:
        ax.axis('off')