A sequence of all sub-proofs including this in post-order, ignoring duplicates.
Iterate over all sub-proofs including this in post-order, ignoring duplicates.
Iterate over all sub-proofs including this in post-order, ignoring duplicates.
Set of all visited sub-proofs including this.
A sequence of all sub-proofs including this in post-order, ignoring duplicates.
Number of sub-proofs including this, not counting duplicates.