def _distance_attribute(self, func, geom=None, tolerance=0.05, spheroid=False, **kwargs):
        # Setting up the distance procedure arguments.
        procedure_args, geo_field = self._spatial_setup(func, field_name=kwargs.get('field_name'))

        # If geodetic defaulting distance attribute to meters (Oracle and
        # PostGIS spherical distances return meters).  Otherwise, use the
        # units of the geometry field.
        connection = connections[self.db]
        geodetic = geo_field.geodetic(connection)
        geography = geo_field.geography

        if geodetic:
            dist_att = 'm'
        else:
            dist_att = Distance.unit_attname(geo_field.units_name(connection))

        # Shortcut booleans for what distance function we're using and
        # whether the geometry field is 3D.
        distance = func == 'distance'
        length = func == 'length'
        perimeter = func == 'perimeter'
        if not (distance or length or perimeter):
            raise ValueError('Unknown distance function: %s' % func)
        geom_3d = geo_field.dim == 3

        # The field's get_db_prep_lookup() is used to get any
        # extra distance parameters.  Here we set up the
        # parameters that will be passed in to field's function.
        lookup_params = [geom or 'POINT (0 0)', 0]

        # Getting the spatial backend operations.
        backend = connection.ops

        # If the spheroid calculation is desired, either by the `spheroid`
        # keyword or when calculating the length of geodetic field, make
        # sure the 'spheroid' distance setting string is passed in so we
        # get the correct spatial stored procedure.
        if spheroid or (backend.postgis and geodetic and
                        (not geography) and length):
            lookup_params.append('spheroid')
        lookup_params = geo_field.get_prep_value(lookup_params)
        params = geo_field.get_db_prep_lookup('distance_lte', lookup_params, connection=connection)

        # The `geom_args` flag is set to true if a geometry parameter was
        # passed in.
        geom_args = bool(geom)

        if backend.oracle:
            if distance:
                procedure_fmt = '%(geo_col)s,%(geom)s,%(tolerance)s'
            elif length or perimeter:
                procedure_fmt = '%(geo_col)s,%(tolerance)s'
            procedure_args['tolerance'] = tolerance
        else:
            # Getting whether this field is in units of degrees since the field may have
            # been transformed via the `transform` GeoQuerySet method.
            srid = self.query.get_context('transformed_srid')
            if srid:
                u, unit_name, s = get_srid_info(srid, connection)
                geodetic = unit_name.lower() in geo_field.geodetic_units

            if geodetic and not connection.features.supports_distance_geodetic:
                raise ValueError(
                    'This database does not support linear distance '
                    'calculations on geodetic coordinate systems.'
                )

            if distance:
                if srid:
                    # Setting the `geom_args` flag to false because we want to handle
                    # transformation SQL here, rather than the way done by default
                    # (which will transform to the original SRID of the field rather
                    #  than to what was transformed to).
                    geom_args = False
                    procedure_fmt = '%s(%%(geo_col)s, %s)' % (backend.transform, srid)
                    if geom.srid is None or geom.srid == srid:
                        # If the geom parameter srid is None, it is assumed the coordinates
                        # are in the transformed units.  A placeholder is used for the
                        # geometry parameter.  `GeomFromText` constructor is also needed
                        # to wrap geom placeholder for SpatiaLite.
                        if backend.spatialite:
                            procedure_fmt += ', %s(%%%%s, %s)' % (backend.from_text, srid)
                        else:
                            procedure_fmt += ', %%s'
                    else:
                        # We need to transform the geom to the srid specified in `transform()`,
                        # so wrapping the geometry placeholder in transformation SQL.
                        # SpatiaLite also needs geometry placeholder wrapped in `GeomFromText`
                        # constructor.
                        if backend.spatialite:
                            procedure_fmt += (', %s(%s(%%%%s, %s), %s)' % (
                                backend.transform, backend.from_text,
                                geom.srid, srid))
                        else:
                            procedure_fmt += ', %s(%%%%s, %s)' % (backend.transform, srid)
                else:
                    # `transform()` was not used on this GeoQuerySet.
                    procedure_fmt = '%(geo_col)s,%(geom)s'

                if not geography and geodetic:
                    # Spherical distance calculation is needed (because the geographic
                    # field is geodetic). However, the PostGIS ST_distance_sphere/spheroid()
                    # procedures may only do queries from point columns to point geometries
                    # some error checking is required.
                    if not backend.geography:
                        if not isinstance(geo_field, PointField):
                            raise ValueError('Spherical distance calculation only supported on PointFields.')
                        if not str(Geometry(six.memoryview(params[0].ewkb)).geom_type) == 'Point':
                            raise ValueError(
                                'Spherical distance calculation only supported with '
                                'Point Geometry parameters'
                            )
                    # The `function` procedure argument needs to be set differently for
                    # geodetic distance calculations.
                    if spheroid:
                        # Call to distance_spheroid() requires spheroid param as well.
                        procedure_fmt += ",'%(spheroid)s'"
                        procedure_args.update({'function': backend.distance_spheroid, 'spheroid': params[1]})
                    else:
                        procedure_args.update({'function': backend.distance_sphere})
            elif length or perimeter:
                procedure_fmt = '%(geo_col)s'
                if not geography and geodetic and length:
                    # There's no `length_sphere`, and `length_spheroid` also
                    # works on 3D geometries.
                    procedure_fmt += ",'%(spheroid)s'"
                    procedure_args.update({'function': backend.length_spheroid, 'spheroid': params[1]})
                elif geom_3d and connection.features.supports_3d_functions:
                    # Use 3D variants of perimeter and length routines on supported backends.
                    if perimeter:
                        procedure_args.update({'function': backend.perimeter3d})
                    elif length:
                        procedure_args.update({'function': backend.length3d})

        # Setting up the settings for `_spatial_attribute`.
        s = {'select_field': DistanceField(dist_att),
             'setup': False,
             'geo_field': geo_field,
             'procedure_args': procedure_args,
             'procedure_fmt': procedure_fmt,
             }
        if geom_args:
            s['geom_args'] = ('geom',)
            s['procedure_args']['geom'] = geom
        elif geom:
            # The geometry is passed in as a parameter because we handled
            # transformation conditions in this routine.
            s['select_params'] = [backend.Adapter(geom)]
        return self._spatial_attribute(func, s, **kwargs)
*session* is the :class:`~ncclient.transport.Session` instance
dataset/ETHPy150Open django/django/django/contrib/gis/db/models/query.py/GeoQuerySet._distance_attribute--crossover with--dataset/ETHPy150Open ncclient/ncclient/ncclient/operations/rpc.py/RPC.__init__