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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 __GetChunk(self, start, end, additional_headers=None):
 """Retrieve a chunk, and return the full response."""

        self.EnsureInitialized()
        request = http_wrapper.Request(url=self.url)
        self.__SetRangeHeader(request, start, end=end)
        if additional_headers is not None:
            request.headers.update(additional_headers)
        return http_wrapper.MakeRequest(
            self.bytes_http, request, retry_func=self.retry_func,
            retries=self.num_retries)