lib/assert.js
function _assert(arg, type, name) {
  name = name || type;
  throw new assert.AssertionError({
    message: util.format('%s (%s) required', name, type),
    actual: typeof (arg),
    expected: type,
    operator: '===',
    stackStartFunction: _assert.caller
  });
}
function _assert(arg, type, name) {
  name = name || type;
  throw new assert.AssertionError({
    message: util.format('%s (%s) required', name, type),
    actual: typeof (arg),
    expected: type,
    operator: '===',
    stackStartFunction: _assert.caller
  });
}
/--- Helpers Copied from mcavage/node-assert-plus