code: function getBrackets() {
    const type = NodeType.BracketsType;
    const token = tokens[pos];
    const line = token.ln;
    const column = token.col;
    const right = token.right;
    let content = [];
  
    // Skip `[`.
    pos++;
  
    if (pos < right) {
      content = getTsets();
    }
  
    const end = getLastPosition(content, line, column, 1);
  
    // Skip `]`.
    pos++;
  
    return newNode(type, content, line, column, end);
  }
docs: Gets node with text inside square brackets, e.g. `[1]`.
  
  @return {!Node}