code: function addAttributes(attrs) {
    _.forEach(attrs, (v, k) => {
      if (v.type !== undefined) {
        this.addAttribute(k, v.type, v.mandatory, v.errorCallback)
      } else {
        this.addAttribute(k, v)
      }
    })
  }
docs: Add several attributes
  @method
  @memberof Class~ClassInstance
  @param {Object} attrs - The attributes to add. The keys are te attribute name,
  the values are the attributes descriptors.
  See {@link Class~ClassInstance#RemoveAttribute} for
  the supported properties.