docs: function Tokenizer(str, tags) {
              this.str = str;
              this.index = 0;
              this.len = str.length;
              this.lineno = 0;
              this.colno = 0;
  
              this.in_code = false;
  
              tags = tags || {};
              this.tags = {
                  BLOCK_START: tags.blockStart || BLOCK_START,
                  BLOCK_END: tags.blockEnd || BLOCK_END,
                  VARIABLE_START: tags.variableStart || VARIABLE_START,
                  VARIABLE_END: tags.variableEnd || VARIABLE_END,
                  COMMENT_START: tags.commentStart || COMMENT_START,
                  COMMENT_END: tags.commentEnd || COMMENT_END
              };
          }