code: def str_args(args):
      
      res = []
      for x in args:
          if isinstance(x, tuple) and len(x) == 2:
              key, value = x
              if value and str_arg(value):
                  res += ["%s=%s" % (key, str_arg(value))]
          else:
              res += [str_arg(x)]
      return ', '.join(res)
docs: formats a list of function arguments prettily not as code
  
      (kwargs are tuples (argname, argvalue)