code: function(attrs) {
          if (_.has(attrs, 'ACL') && !(attrs.ACL instanceof AV.ACL)) {
            throw new AVError(AVError.OTHER_CAUSE, 'ACL must be a AV.ACL.');
          }
        }
docs: You should not call this function directly unless you subclass
  <code>AV.Object</code>, in which case you can override this method
  to provide additional validation on <code>set</code> and
  <code>save</code>.  Your implementation should throw an Error if
  the attrs is invalid
  
  @param {Object} attrs The current data to validate.
  @see AV.Object#set