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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 _set(self, key, value, identity='image'):
 """ Serializing, prefix wrapper for _set_raw """

        if identity == 'image':
            s = serialize_image_file(value)
        else:
            s = serialize(value)
        self._set_raw(add_prefix(key, identity), s)