isUnicode = function (operator, previous) {
  if (operator === '+') {

    // Catch the following:
    // @font-face {
    //   unicode-range: U+26;
    // }
    if (previous && previous.is('ident') && previous.content === 'U') {
      return true;
    }
  }

  return false;
}
Determine if operator is part of unicode

@param {string} operator - The operator
@param {Object} previous - The previous node
@returns {bool} true / false