code: function getBlock() {
    const type = NodeType.BlockType;
    const token = tokens[pos];
    const line = token.ln;
    const column = token.col;
    const end = tokens[pos].right;
    let content = [];
  
    // Skip `{`.
    pos++;
  
    while (pos < end) {
      if (checkBlockdecl(pos)) content = content.concat(getBlockdecl());
      else throwError(pos);
    }
  
    const end_ = getLastPosition(content, line, column, 1);
    pos = end + 1;
  
    return newNode(type, content, line, column, end_);
  }
docs: Get node with a block
  @returns {Array} `['block', x]`