<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def geo_field(queryset):
 """Returns the GeometryField for a django or spillway GeoQuerySet."""

    for field in queryset.model._meta.fields:
        if isinstance(field, models.GeometryField):
            return field
    raise exceptions.FieldDoesNotExist('No GeometryField found')