def search(self, regex):
        try:
            spec = {'$or': [{'data.content'    : {'$regex': regex, '$options': 'im'}},
                            {'data.description': {'$regex': regex, '$options': 'im'}}]}
            fields = {'_id': 0}
            cur = self.db.docs.find(spec, fields)
        except Exception as e:
            raise DatabaseException(e)
        return [Document(**row) for row in cur]
def forcedens_surface(fdens, ax=0):
    if ax == 0:
        _create_3d_axis()
        ax = plt.gca()
    xpos = [p for p in fdens.positions[0]['X']]
    ypos = [p['position'] for p in fdens.positions]
    z = 1e-3*np.array([p['FN']
                       for p in fdens.positions])
    _plot_surface(ax, xpos, ypos, z,
                  (u'Rotor pos/°', u'Pos/°', u'F N / kN/m²'))