docs: def _module_name(filename):
          """
          Try to find a module name for a file path
          by stripping off a prefix found in sys.modules.
          """
  
          absfile = os.path.abspath(filename)
          match = filename
  
          for base in [''] + sys.path:
              base = os.path.abspath(base)
              if absfile.startswith(base):
                  match = absfile[len(base):]
                  break
  
          return SUFFIX_RE.sub('', match).lstrip('/').replace('/', '.')