```ruby
module Onfido
  class API
    def initialize(options = {})
      @api_key = options[:api_key]
    end

    def method_missing(method, *args)
      klass = method.to_s.split('_').collect(&:capitalize).join
      Object.const_get("Onfido::#{klass}").new(@api_key)
    rescue NameError
      super
    end

    def respond_to_missing?(method, include_private = false)
      klass = method.to_s.capitalize
      Object.const_get("Onfido::#{klass}")
      true
    rescue NameError
      super
    end
  end
end
```

Replace method_missing with explicit methods
user
```ruby
module Onfido
  class API
    def initialize(options = {})
      @api_key = options[:api_key]
    end

    def applicant
      Onfido::Applicant.new(@api_key)
    end

    def check
      Onfido::Check.new(@api_key)
    end

    def document
      Onfido::Document.new(@api_key)
    end

    def live_photo
      Onfido::LivePhoto.new(@api_key)
    end

    def report
      Onfido::Report.new(@api_key)
    end

    def report_type_group
      Onfido::ReportTypeGroup.new(@api_key)
    end

    def sdk_token
      Onfido::SdkToken.new(@api_key)
    end

    def webhook
      Onfido::Webhook.new(@api_key)
    end

    def address
      Onfido::Address.new(@api_key)
    end
  end
end
```
assistant