def recode! dt=nil, &block
      return to_enum(:recode!) unless block_given?

      @data.map!(&block).data
      @data = cast_vector_to(dt || @dtype)
      self
    end
def recode! dt=nil, &block
      return to_enum(:recode!) unless block_given?

      @data.map!(&block).data
      @data = cast_vector_to(dt || @dtype)
      self
    end
Destructive version of recode!