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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def columnSchema(self):
 """ Returns the schema for the image column. :return: a :class:`StructType` for image column, ``struct<origin:string, height:int, width:int, nChannels:int, mode:int, data:binary>``. .. versionadded:: 2.4.0 """


        if self._columnSchema is None:
            ctx = SparkContext._active_spark_context
            jschema = ctx._jvm.org.apache.spark.ml.image.ImageSchema.columnSchema()
            self._columnSchema = _parse_datatype_json_string(jschema.json())
        return self._columnSchema