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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 image_files_download(self, image_id):
 """Get data file for image with given identifier. Parameters image_id : string Unique image identifier Returns ------- FileInfo Information about image file on disk or None if identifier is unknown """

        # Retrieve image to ensure that it exist
        img = self.image_files_get(image_id)
        if img is None:
            # Return None if image is unknown
            return None
        else:
            # Reference and information for original uploaded file
            return FileInfo(
                img.image_file,
                img.properties[datastore.PROPERTY_MIMETYPE],
                img.properties[datastore.PROPERTY_FILENAME]
            )