code: def unique(self, name):
      
      # Make sure the name is valid
      name = self.valid(name)
      # Make sure it's not too long
      name = self.trim(name)
      # Now make sure it's unique
      unique_name = name
      i = 2
      while unique_name in self.names:
        unique_name = name + str(i)
        i += 1
      self.names.add(unique_name)
      return unique_name
docs: Make a variable name unique by appending a number if needed.