def transform_values(&b)
            self.class.new self.map { |k, v|
                [ k.to_sym, b.call(v) ]
            }.to_h
        end
def transform_values(&b)
            self.class.new self.map { |k, v|
                [ k.to_sym, b.call(v) ]
            }.to_h
        end
Returns a new Dictionary object with values modified by given block.