def insert(index, v)
      DataTypeValidator.validate :SimpleTypedList_insert, @allowed_types, v
      raise ArgumentError, "Item is protected and cannot be changed" if protected? index
      @list.insert(index, v)
      v
    end
inserts an item at the index specfied
@param [Integer] index
@param [Any] v
@raise [ArgumentError] if the index is protected by locking
@raise [ArgumentError] if the index is not one of the allowed types