code: def hist_calls(fn):
      
      @functools.wraps(fn)
      def wrapper(*args, **kwargs):
          _histogram = histogram(
              "%s_calls" % pyformance.registry.get_qualname(fn))
          rtn = fn(*args, **kwargs)
          if type(rtn) in (int, float):
              _histogram.add(rtn)
          return rtn
      return wrapper
docs: Decorator to check the distribution of return values of a function.