code: func (p *Parser) parseLeftDelim(cur *ListNode) error {
  	p.pos += len(leftDelim)
  	p.consumeText()
  	newNode := newList()
  	cur.append(newNode)
  	cur = newNode
  	return p.parseInsideAction(cur)
  }
docs: // parseLeftDelim scans the left delimiter, which is known to be present.