old_contents: from django.contrib.gis.db.models.functions import GeoFunc
  from django.db.models import CharField, FloatField, Func
  
  
  class Length(GeoFunc):
      """ ST_Length postgis function """
      output_field = FloatField()
  
  
  class GeometryType(Func):
      """
      GeometryType postgis function
      """
      output_field = CharField()
      function = 'GeometryType'
  
new_contents: from django.contrib.gis.db.models.functions import GeoFunc
  from django.db.models import CharField, FloatField
  
  
  class Length(GeoFunc):
      """ ST_Length postgis function """
      output_field = FloatField()
  
  
  class GeometryType(GeoFunc):
      """
      GeometryType postgis function
      """
      output_field = CharField()
      function = 'GeometryType'
  
subject: Change func for geofunc