code: def imageFields(self):
          
  
          if self._imageFields is None:
              ctx = SparkContext._active_spark_context
              self._imageFields = list(ctx._jvm.org.apache.spark.ml.image.ImageSchema.imageFields())
          return self._imageFields
docs: Returns field names of image columns.
  
          :return: a list of field names.
  
          .. versionadded:: 2.3.0