块样式映射

使用隐式键：

key: value
another key:
  - some
  - more
  - values
[1, 2, 3]: last value, which has a flow style key

使用隐式和显式键：

? key
: value
another key:
  - some
  - more
  - values
? [1, 2, 3]
: last value, which has a flow style key

key，another key 和 [1, 2, 3] 是相同映射的键，尽管它们使用不同的键样式。

嵌套映射：

first level:
  second level:
    ? third level
    :
      forth level: value of implicit key
    ? third level, second key
    : value of explicit key
  ?
    mapping as: key of
    another: mapping
  : scalar value of mapping key
first level, second key:
  last value