dump different scalar styles in the same document in PyYAML

Hi All,
even though there is plenty of options while dumping YAML in PyYAML, I
could not find how I can mix different scalar styles in the same
document.
For instance, instead of:
---
value1: 1
value2: 'line1

    line2

   line3'
...
I would like to dump
---
value1: 1
value2: |-
    line1
    line2
    line3
...

So I would like to use the plain scalar style but if the value
contains '\n' then the literal style shall be used.
Is it possible?

Andrey

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