transform_keys

# File activesupport/lib/active_support/hash_with_indifferent_access.rb, line 354
    def transform_keys(hash = NOT_GIVEN, &block)
      if NOT_GIVEN.equal?(hash)
        if block_given?
          self.class.new(super(&block))
        else
          to_enum(:transform_keys)
        end
      else
        self.class.new(super)
      end
    end