1---
2- &CENTER { x: 1, 'y': 2 }
3- &LEFT { x: 0, 'y': 2 }
4- &BIG { r: 10 }
5- &SMALL { r: 1 }
6
7# All the following maps are equal:
8
9- # Explicit keys
10  x: 1
11  'y': 2
12  r: 10
13  label: center/big
14
15- # Merge one map
16  << : *CENTER
17  r: 10
18  label: center/big
19
20- # Merge multiple maps
21  << : [ *CENTER, *BIG ]
22  label: center/big
23
24- # Override
25  << : [ *BIG, *LEFT, *SMALL ]
26  x: 1
27  label: center/big
28