code: def insert(self, i, x):
          
          if not isinstance(x, str):
              raise TypeError(
                  'Members of this object must be strings. '
                  'You supplied \"%s\"' % type(x))
          list.insert(self, i, x)
docs: s.insert(i, x) same as s[i:i] = [x]
          Raises TypeError if x isn't a string.