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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 textFileStream(self, directory, process_all=False):
 """Monitor a directory and process all text files. File names starting with ``.`` are ignored. :param string directory: a path :param bool process_all: whether to process pre-existing files :rtype: DStream .. warning:: The ``process_all`` parameter does not exist in the PySpark API. """

        deserializer = FileTextStreamDeserializer(self._context)
        file_stream = FileStream(directory, process_all)
        self._on_stop_cb.append(file_stream.stop)
        return DStream(file_stream, self, deserializer)