* @param act The 'acquire' action that may read from a release sequence
* @param release_heads A pass-by-reference return parameter. Will be filled
* with the head(s) of the release sequence(s), if they exists with certainty.
* @param act The 'acquire' action that may read from a release sequence
* @param release_heads A pass-by-reference return parameter. Will be filled
* with the head(s) of the release sequence(s), if they exists with certainty.