Aliases & Anchors
- You can attach an &anchor to any node
 - This includes mapping keys
 - You can refer to it with an *alias
 - The anchor must be followed by a line break unless the node is a scalar
 - js-yaml has problems with mapping key anchors
 
---
a mapping: &map
  &key a: &value b
the same mapping: *map
key a: *key
value b: *value