Returns the image schema.

        :return: a :class:`StructType` with a single column of images
               named "image" (nullable) and having the same type returned by :meth:`columnSchema`.

        .. versionadded:: 2.3.0

def imageSchema(self):
        """
        Returns the image schema.

        :return: a :class:`StructType` with a single column of images
               named "image" (nullable) and having the same type returned by :meth:`columnSchema`.

        .. versionadded:: 2.3.0
        """

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