module Mo
  MAPPING = { a: 'a', b: 'b' }
  @mapping = 'ayza2'
  class << self
    @mapping_singleton = 'ayza'
    def test
      a = :a
      p MAPPING.dig(a)
      p @mapping
    end
  end

  def test2
    p MAPPING
  end
end


Mo.test

# Mo::test2

p Mo.singleton_class.instance_variables
p Mo.instance_variables