code: def _format_trace(trace):
      
      lines = []
      for fname, lineno, func, src, _ in trace:
          if src:
              for line in src:
                  lines.append('    '+line.strip()+'\n')
          lines.append('  %s:%4d in %s\n' % (fname, lineno, func))
      return ''.join(lines)
docs: Convert the (stripped) stack-trace to a nice readable format. The stack
      trace `trace` is a list of frame records as returned by
      **inspect.stack** but without the frame objects.
      Returns a string.