def unique_id
      generator = Sass::Script::Functions.random_number_generator
      Thread.current[:sass_last_unique_id] ||= generator.rand(36**8)
      # avoid the temptation of trying to guess the next unique value.
      value = (Thread.current[:sass_last_unique_id] += (generator.rand(10) + 1))
      # the u makes this a legal identifier if it would otherwise start with a number.
      identifier("u" + value.to_s(36).rjust(8, '0'))
    end
def unique_id
      generator = Sass::Script::Functions.random_number_generator
      Thread.current[:sass_last_unique_id] ||= generator.rand(36**8)
      # avoid the temptation of trying to guess the next unique value.
      value = (Thread.current[:sass_last_unique_id] += (generator.rand(10) + 1))
      # the u makes this a legal identifier if it would otherwise start with a number.
      identifier("u" + value.to_s(36).rjust(8, '0'))
    end
Returns a unique CSS identifier. The identifier is returned as an unquoted
 string. The identifier returned is only guaranteed to be unique within the
 scope of a single Sass run.

 @overload unique_id()
 @return [Sass::Script::Value::String]