Controlling YAML dump format

[gga]

I was wondering if Ruby's YAML format offered some control on the
preferred YAML dump format syntax. I cannot find much on it.

For example, arrays in YAML can be spit out as either:

actions: [ ONE, TWO ]

instead of ruby's yaml format of:

actions:
- ONE
- TWO

Ruby's YAML will read both syntaxes, but dump() seems to only know
about one.