Ruby modules displaying inexplicit dependencies

gistfile1.rb

module MyFirstModule
  def first_public_method(my_string)
    second_public_method(my_string)
  end
end

module MySecondModule
  def second_public_method(my_string)
    return "#{my_string} 1"
  end
end

class MyClass
  include MyFirstModule
  include MySecondModule
end

puts MyClass.new.first_public_method("hey") # => "hey 1"