@ DocumentNode (location: (1:0)-(7:0))
└── children: (2 items)
    ├── @ HTMLElementNode (location: (1:0)-(6:5))
    │   ├── open_tag:
    │   │   └── @ HTMLOpenTagNode (location: (1:0)-(4:1))
    │   │       ├── tag_opening: "<" (location: (1:0)-(1:1))
    │   │       ├── tag_name: "h1" (location: (1:1)-(1:3))
    │   │       ├── tag_closing: ">" (location: (4:0)-(4:1))
    │   │       ├── children: (2 items)
    │   │       │   ├── @ HTMLAttributeNode (location: (2:2)-(2:13))
    │   │       │   │   ├── name:
    │   │       │   │   │   └── @ HTMLAttributeNameNode (location: (2:2)-(2:4))
    │   │       │   │   │       └── name: "id" (location: (2:2)-(2:4))
    │   │       │   │   │
    │   │       │   │   ├── equals: "=" (location: (2:4)-(2:5))
    │   │       │   │   └── value:
    │   │       │   │       └── @ HTMLAttributeValueNode (location: (2:5)-(2:13))
    │   │       │   │           ├── open_quote: """ (location: (2:5)-(2:6))
    │   │       │   │           ├── children: (1 item)
    │   │       │   │           │   └── @ LiteralNode (location: (2:6)-(2:12))
    │   │       │   │           │       └── content: "header"
    │   │       │   │           │
    │   │       │   │           ├── close_quote: """ (location: (2:12)-(2:13))
    │   │       │   │           └── quoted: true
    │   │       │   │
    │   │       │   │
    │   │       │   └── @ HTMLAttributeNode (location: (3:2)-(3:23))
    │   │       │       ├── name:
    │   │       │       │   └── @ HTMLAttributeNameNode (location: (3:2)-(3:7))
    │   │       │       │       └── name: "class" (location: (3:2)-(3:7))
    │   │       │       │
    │   │       │       ├── equals: "=" (location: (3:7)-(3:8))
    │   │       │       └── value:
    │   │       │           └── @ HTMLAttributeValueNode (location: (3:8)-(3:23))
    │   │       │               ├── open_quote: """ (location: (3:8)-(3:9))
    │   │       │               ├── children: (1 item)
    │   │       │               │   └── @ LiteralNode (location: (3:9)-(3:22))
    │   │       │               │       └── content: "class1 class2"
    │   │       │               │
    │   │       │               ├── close_quote: """ (location: (3:22)-(3:23))
    │   │       │               └── quoted: true
    │   │       │
    │   │       │
    │   │       └── is_void: false
    │   │
    │   ├── tag_name: "h1" (location: (1:1)-(1:3))
    │   ├── body: (1 item)
    │   │   └── @ HTMLTextNode (location: (4:1)-(6:0))
    │   │       └── content: "\n  Content\n"
    │   │
    │   ├── close_tag:
    │   │   └── @ HTMLCloseTagNode (location: (6:0)-(6:5))
    │   │       ├── tag_opening: "</" (location: (6:0)-(6:2))
    │   │       ├── tag_name: "h1" (location: (6:2)-(6:4))
    │   │       └── tag_closing: ">" (location: (6:4)-(6:5))
    │   │
    │   └── is_void: false
    │
    └── @ HTMLTextNode (location: (6:5)-(7:0))
        └── content: "\n"