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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 _refresh_context(self):
 """ Get current facade segment. To prevent resource leaking in Lambda worker, every time there is segment present, we compare its trace id to current environment variables. If it is different we create a new facade segment and clean up subsegments stored. """

        header_str = os.getenv(LAMBDA_TRACE_HEADER_KEY)
        trace_header = TraceHeader.from_header_str(header_str)
        if not global_sdk_config.sdk_enabled():
            trace_header._sampled = False

        segment = getattr(self._local, 'segment', None)

        if segment:
            # Ensure customers don't have leaked subsegments across invocations
            if not trace_header.root or trace_header.root == segment.trace_id:
                return
            else:
                self._initialize_context(trace_header)
        else:
            self._initialize_context(trace_header)