parameters: (self, frame, event, arg)
return_statement: return fn
docstring: Called on new threads, installs the real tracer.
docstring_summary: Called on new threads, installs the real tracer.
docstring_tokens: Called on new threads installs the real tracer .
function: def _installation_trace(self, frame, event, arg):
          """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, event, arg)
          # Return the new trace function to continue tracing in this scope.
          return fn
function_tokens: def _installation_trace ( self , frame , event , arg ) : # 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 , event , arg ) # Return the new trace function to continue tracing in this scope. return fn