Returns a fields dict for this serializer with a 'geometry' field
        added.

def get_fields(self):
        """Returns a fields dict for this serializer with a 'geometry' field
        added.
        """
        fields = super(GeoModelSerializer, self).get_fields()
        # Set the geometry field name when it's undeclared.
        if not self.Meta.geom_field:
            for name, field in fields.items():
                if isinstance(field, GeometryField):
                    self.Meta.geom_field = name
                    break
        return fields