def extract_const(class_name)
      class_name.split('::').reduce(FiniteMachine) do |constant, part|
        constant.const_get(part)
      end
    end
def extract_const(class_name)
      class_name.split('::').reduce(FiniteMachine) do |constant, part|
        constant.const_get(part)
      end
    end
Find constant in state machine namespace

 @param [String] class_name

 @api private