code: def start_trace(reset=True, filter_func=None, time_filter_func=None):
      
      global trace_filter
      global time_filter
      if reset:
          reset_trace()
  
      if filter_func:
          trace_filter = filter_func
      else:
          trace_filter = GlobbingFilter(exclude=['pycallgraph.*'])
  
      if time_filter_func:
          time_filter = time_filter_func
      else:
          time_filter = GlobbingFilter()
  
      sys.settrace(tracer)
docs: Begins a trace. Setting reset to True will reset all previously recorded
      trace data. filter_func needs to point to a callable function that accepts
      the parameters (call_stack, module_name, class_name, func_name, full_name).
      Every call will be passed into this function and it is up to the function
      to decide if it should be included or not. Returning False means the call
      will be filtered out and not included in the call graph.