```
doc
 |- doc/                   # Documentation tree
 |   |- category/          # Child node
 |   |   |- _index.yaml    # Node information
 |   |   |- item1.yaml     # Item data
 |   |   |- item1.01.md    # Item extra file
 |   |- _index.yaml        # Node information
 |   |- _index.01.md       # Node extra file
 |   |- _index.01.txt      # Node extra file
 |   |- _index.01.pug      # Node extra file
 |   |- _index.01.svg      # Node extra file
 |- templates/             # Pug Templates
 |   |- template1.pug      # A pugjs template
 |   |- template2.pug      # A pugjs template
 |- doc.yaml               # Documentation main file
```
