Cannot get the dns verification working following the steps on README.md

[chekkan]

I've got a file at libraries/acme_dns.rb with the content from the readme file defining the install_dns_challenge method and remove_dns_challenge. Using in my recipe with resource acme_certificate.

include_recipe 'acme::default'

apitoken = chef_vault_item('secrets', 'tokens')['dns_provider_token']

include_recipe 'prometheus::use_lwrp'

acme_certificate node['fqdn'] do
  key "/path/to/key.key"
  crt "//path/to/cert.crt"
  install_authz_block install_dns_challenge(apitoken)
  remove_authz_block remove_dns_challenge(apitoken)
end

But, I am getting the following error...

Failure/Error: ChefSpec::SoloRunner.new(platform: 'ubuntu', version: '22.04').converge(described_recipe)
     NoMethodError:
       undefined method `install_dns_challenge' for Custom resource acme_certificate from cookbook acme

           raise NoMethodError, "undefined method `#{method_symbol}' for #{self.class}"
           ^^^^^

chef --version
Chef Workstation version: 24.4.1064
Test Kitchen version: 3.6.0
Cookstyle version: 7.32.8
Chef Infra Client version: 18.4.12
Chef InSpec version: 5.22.40
Chef CLI version: 5.6.14
Chef Habitat version: 1.6.652

I am new to chef and ruby. Perhaps I am not getting how the helper method is supposed to be used.