def validate_requirements(args)
            errors = []
            @require_set.each do |req, sets|
                sets.each do |set|
                    count = set.count{ |arg| args.has_key?(arg.key) && args[arg.key] }
                    case req
                    when :one
                        if count == 0
                            errors << "No argument has been specified for one of: #{set.join(', ')}"
                        elsif count > 1
                            errors << "Only one argument can been specified from: #{set.join(', ')}"
                        end
                    when :any
                        if count == 0
                            errors << "At least one of the arguments must be specified from: #{set.join(', ')}"
                        end
                    end
                end
            end
            errors
        end
def validate_requirements(args)
            errors = []
            @require_set.each do |req, sets|
                sets.each do |set|
                    count = set.count{ |arg| args.has_key?(arg.key) && args[arg.key] }
                    case req
                    when :one
                        if count == 0
                            errors << "No argument has been specified for one of: #{set.join(', ')}"
                        elsif count > 1
                            errors << "Only one argument can been specified from: #{set.join(', ')}"
                        end
                    when :any
                        if count == 0
                            errors << "At least one of the arguments must be specified from: #{set.join(', ')}"
                        end
                    end
                end
            end
            errors
        end
Validates the supplied +args+ Hash object, verifying that any argument
 set requirements have been satisfied. Returns an array of error
 messages for each set requirement that is not satisfied.

 @param args [Hash] a Hash containing the keys and values identified
   by the parser.
 @return [Array] a list of errors for any argument requirements that
   have not been satisfied.