code: function(type, pre, post, onlyInDefault) {
      if (type !== 'attribute' && type !== 'text') {
        throw new TypeError('Expression delimiters must be of type "attribute" or "text"');
      }
  
      this.binders[type]._expr = new RegExp(escapeRegExp(pre) + '(.*?)' + escapeRegExp(post), 'g');
      if (type === 'attribute') {
        this.binders[type]._delimitersOnlyInDefault = !!onlyInDefault;
      }
    }
docs: Sets the delimiters that define an expression. Default is `{{` and `}}` but this may be overridden. If empty
  strings are passed in (for type "attribute" only) then no delimiters are required for matching attributes, but the
  default attribute matcher will not apply to the rest of the attributes. TODO support different delimiters for the
  default attributes vs registered ones (i.e. allow regular attributes to use {{}} when bound ones do not need them)