code: def grep_param_names(self, regexp):
          
          if not isinstance(regexp, _pattern_type): regexp = compile(regexp)
          found_params = []
          def visit(innerself, regexp):
              if (innerself is not self) and regexp.match(innerself.hierarchy_name().partition('.')[2]):
                  found_params.append(innerself)
          self.traverse(visit, regexp)
          return found_params
docs: create a list of parameters, matching regular expression regexp