code: def _add_file_mask(self, start, method_str, method):
          
          fm = self._f_mask.get(method_str, [])
          fm.append((start, method))
          fm.sort(key=lambda k: len(k[0]), reverse=True)
          self._f_mask[method_str] = fm
          self._f_argc[method_str] = None
docs: Adds a raw file mask for dynamic requests.
  
          Parameters
          ----------
          start : string
              The URL prefix that must be matched to perform this request.
  
          method_str : string
              The HTTP method for which to trigger the request.
  
          method : function(esrh, args)
              The function to execute to perform the request. The function takes
              two arguments. esrh is the QuickServerRequestHandler object that
              called the function. args is a map containing the arguments to the
              request (i.e., the rest of the URL as path segment array 'paths', a
              map of all query fields / flags 'query', the fragment string
              'fragment', and if the method was a POST the JSON form content
              'post'). The function must return a file object containing the
              response (preferably BytesIO). If the result is None no response
              body is sent. In this case make sure to send an appropriate error
              code.