code: def format_pattrs(pattrs: List['api.PrettyAttribute']) -> str:
      
      output = []
      pattrs.sort(
          key=lambda x: (
              _FORMATTER[x.display_group].display_index,
              x.display_group,
              x.name,
          )
      )
      for display_group, grouped_pattrs in groupby(pattrs, lambda x: x.display_group):
          output.append(
              _FORMATTER[display_group].formatter(display_group, grouped_pattrs)
          )
  
      return '\n'.join(output)
docs: Generates repr string given a list of pattrs.