code: def show_diff(
      self, location: tuple[str, int] | None = None
  ) -> list[str]:
      new_lines = self.read_file(self.filename)
      old_filename = self.options["diff"]
      old_lines = self.read_file(old_filename)
      diff = unified_diff(
          old_lines, new_lines, str(old_filename), str(self.filename)
      )
      return list(diff)
  
imports: from __future__ import annotations
  import sys
  import textwrap
  from difflib import unified_diff
  from typing import TYPE_CHECKING, Any
  from docutils import nodes
  from docutils.parsers.rst import directives
  from docutils.statemachine import StringList
  from sphinx import addnodes
  from sphinx.directives import optional_int
  from sphinx.locale import __
  from sphinx.util import logging, parselinenos
  from sphinx.util.docutils import SphinxDirective
label_desc: Use image node_id 5 for calling the LiteralIncludeReader obj's underlying member method code with example usage: obj.show_diff(location) and returns: list