docs: def render(self, mark_lib=True):
          """Render a single frame in a traceback."""
          return FRAME_HTML % {
              "id": self.id,
              "filename": escape(self.filename),
              "lineno": self.lineno,
              "function_name": escape(self.function_name),
              "lines": self.render_line_context(),
              "library": "library" if mark_lib and self.is_library else "",
          }