Return True if all previous COMMITs have been ordered

def all_prev_ordered(self, commit: Commit):
        """
        Return True if all previous COMMITs have been ordered
        """
        # TODO: This method does a lot of work, choose correct data
        # structures to make it efficient.

        viewNo, ppSeqNo = commit.viewNo, commit.ppSeqNo

        if self.last_ordered_3pc == (viewNo, ppSeqNo - 1):
            # Last ordered was in same view as this COMMIT
            return True

        # if some PREPAREs/COMMITs were completely missed in the same view
        toCheck = set()
        toCheck.update(set(self.sentPrePrepares.keys()))
        toCheck.update(set(self.prePrepares.keys()))
        toCheck.update(set(self.prepares.keys()))
        toCheck.update(set(self.commits.keys()))
        for (v, p) in toCheck:
            if v < viewNo and (v, p) not in self.ordered:
                # Have commits from previous view that are unordered.
                return False
            if v == viewNo and p < ppSeqNo and (v, p) not in self.ordered:
                # If unordered commits are found with lower ppSeqNo then this
                # cannot be ordered.
                return False

        return True