code: def _arg_repr(self, arg):
          
          r = repr(arg)
          max = 40
          if len(r) > max:
              if hasattr(arg, 'shape'):
                  r = 'array:' + 'x'.join([repr(s) for s in arg.shape])
              else:
                  r = r[:max-3] + '...'
          return r
docs: Get a useful (and not too large) represetation of an argument.