# File lib/rake_remote_task.rb, line 411
  def self.role role_name, host, args = {}
    [*host].each do |hst|
      raise ArgumentError, "invalid host: #{hst}" if hst.nil? or hst.empty?
    end
    @@roles[role_name] = {} if @@def_role_hash.eql? @@roles[role_name]
    @@roles[role_name][host] = args
  end