# File lib/mcollective/ddl/base.rb, line 191
      def requires(requirement)
        raise "Requirement should be a hash in the form :item => 'requirement'" unless requirement.is_a?(Hash)

        valid_requirements = [:mcollective]

        requirement.keys.each do |key|
          unless valid_requirements.include?(key)
            raise "Requirement %s is not a valid requirement, only %s is supported" % [key, valid_requirements.join(", ")]
          end

          @requirements[key] = requirement[key]
        end

        validate_requirements
      end