Address comments

torch_geometric/data/hetero_data.py

@@ -796,7 +796,7 @@ def is_sorted_by_time(
         if not types:
             return False
 
-        for t in [self._to_canonical(t) for t in types]:
+        for t in types:
             if 'time' not in self[t]:
                 return False
             if not self[t].is_sorted_by_time():
@@ -813,8 +813,7 @@ def sort_by_time(self, types: Union[List[EdgeType],
             return self
 
         out = copy.copy(self)
-        # TODO: should we limit `out` to be a [edge|node]_type_subgraph?
-        for t in [self._to_canonical(t) for t in types]:
+        for t in types:
             out[t].sort_by_time()
         return out
 
@@ -828,8 +827,7 @@ def snapshot(self, types: Union[List[EdgeType], List[NodeType]],
             return self
 
         out = copy.copy(self)
-        # TODO: should we limit `out` to be a [edge|node]_type_subgraph?
-        for t in [self._to_canonical(t) for t in types]:
+        for t in types:
             out[t].snapshot(start_time, end_time)
         return out
 
@@ -842,8 +840,7 @@ def up_to(self, types: Union[List[EdgeType], List[NodeType]],
             return self
 
         out = copy.copy(self)
-        # TODO: should we limit `out` to be a [edge|node]_type_subgraph?
-        for t in [self._to_canonical(t) for t in types]:
+        for t in types:
             out[t].up_to(end_time)
         return out