After upgrading from 0.4.0 to 0.10.0 I had to (locally) change this line:

# from:
Optional[Array[String[1]]]     $labels                = undef,
# to
Optional[Array[String]]        $labels                = undef,

There seemed to be no way to specify labels.
I'm guessing that a valid parameter would be:

[ ['one'], ['two'] ]

but what it would actually do with it I did not check. After correcting the code, I was able to use a flat array as a parameter:

[ 'one', 'two' ]