class Shoulda::Matchers::ActiveModel::ValidatePresenceOfMatcher

def suggestions_for_belongs_to
  if belongs_to_association_configured_to_be_required?
    <<~MESSAGE
      one of the following instead, depending on your use case:
            #{example_of_belongs_to(with: [:optional, false])}
            #{example_of_belongs_to(with: [:required, true])}
    MESSAGE
  else
    <<~MESSAGE
      the following instead:
            #{example_of_belongs_to}
    MESSAGE
  end
end