code: def get_lines_from_file(filename, lineno, context_lines):
      
  
      def get_lines(start, end):
          return [linecache.getline(filename, l).rstrip() for l in range(start, end)]
  
      lower_bound = max(1, lineno - context_lines)
      upper_bound = lineno + context_lines
      linecache.checkcache(filename)
      pre_context = get_lines(lower_bound, lineno)
      context_line = linecache.getline(filename, lineno).rstrip()
      post_context = get_lines(lineno + 1, upper_bound)
      return lower_bound, pre_context, context_line, post_context
docs: Returns context_lines before and after lineno from file.
      Returns (pre_context_lineno, pre_context, context_line, post_context).