virtualEnvironment/lib/python2.7/site-packages/coverage/collector.py
def _installation_trace(self, frame_unused, event_unused, arg_unused):
        """Called on new threads, installs the real tracer."""
        # Remove ourselves as the trace function
        sys.settrace(None)
        # Install the real tracer.
        fn = self._start_tracer()
        # Invoke the real trace function with the current event, to be sure
        # not to lose an event.
        if fn:
            fn = fn(frame_unused, event_unused, arg_unused)
        # Return the new trace function to continue tracing in this scope.
        return fn
def _installation_trace(self, frame_unused, event_unused, arg_unused):
        """Called on new threads, installs the real tracer."""
        # Remove ourselves as the trace function
        sys.settrace(None)
        # Install the real tracer.
        fn = self._start_tracer()
        # Invoke the real trace function with the current event, to be sure
        # not to lose an event.
        if fn:
            fn = fn(frame_unused, event_unused, arg_unused)
        # Return the new trace function to continue tracing in this scope.
        return fn
Called on new threads, installs the real tracer.