Populates this graph from the given one based on affected_files

def populate_from_trace_graph(self, graph: TraceGraph) -> None:
        """Populates this graph from the given one based on affected_files
        """
        # Track which trace frames have been visited as we populate the full
        # traces of the graph.
        self._visited_trace_frame_ids: Set[int] = set()

        self._populate_affected_issues(graph)

        if not self._affected_issues_only:
            # Finds issues from the conditions and saves them.
            # Also saves traces that have been trimmed to the affected
            # conditions.
            self._populate_issues_from_affected_trace_frames(graph)

            # Traces populated above may be missing all traces because
            # _populate_issues_from_affected_trace_frames only populates
            # traces that reach the affected conditions in one direction. We
            # may need to populate traces in other directions too.
            #
            # For example:
            #
            # Issue_x reaches affected_file_x via postcondition_x (forward
            # trace, i.e. trace leading to source). None of its backward
            # traces (leading to sinks) reach the affected files.
            #
            # _populate_issues_from_affected_trace_frames would have copied its
            # forward traces and trimmed it to those reaching postcondition_x.
            # We cannot blindly populate all forward traces in this case as
            # branches not leading to postcondition_x are unnecessary.
            #
            # However, in this specific example, all backward traces are needed
            # to give a complete picture of which sinks the issue reaches.
            # The following ensures that.
            for instance_id in self._issue_instances.keys():
                first_hop_ids = self._issue_instance_trace_frame_assoc[instance_id]
                fwd_trace_ids = {
                    tf_id
                    for tf_id in first_hop_ids
                    if self._trace_frames[tf_id].kind == TraceKind.POSTCONDITION
                }
                bwd_trace_ids = {
                    tf_id
                    for tf_id in first_hop_ids
                    if self._trace_frames[tf_id].kind == TraceKind.PRECONDITION
                }

                if len(fwd_trace_ids) == 0:
                    self._populate_issue_trace(
                        graph, instance_id, TraceKind.POSTCONDITION
                    )

                if len(bwd_trace_ids) == 0:
                    self._populate_issue_trace(
                        graph, instance_id, TraceKind.PRECONDITION
                    )