Moved around imports in PostGIS operations

from django.conf import settings

from django.contrib.gis.db.backends.base.operations import \

    BaseSpatialOperations

from django.contrib.gis.db.backends.postgis.adapter import PostGISAdapter

from django.contrib.gis.db.backends.postgis.pgraster import (

    from_pgraster, to_pgraster,

)

from django.contrib.gis.db.backends.utils import SpatialOperator

from django.contrib.gis.geometry.backend import Geometry

from django.contrib.gis.measure import Distance

from django.db.utils import ProgrammingError

from django.utils.functional import cached_property

from .adapter import PostGISAdapter

from .models import PostGISGeometryColumns, PostGISSpatialRefSys

from .pgraster import get_pgraster_srid

from .pgraster import from_pgraster, get_pgraster_srid, to_pgraster

class PostGISOperator(SpatialOperator):