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)
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.