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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 imageFields(self):
 """ Returns field names of image columns. :return: a list of field names. .. versionadded:: 2.3.0 """


        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