fix(trace-view): Doing the TODO that was waiting on py 3.7+
diff --git a/src/sentry/api/endpoints/organization_events_trace.py b/src/sentry/api/endpoints/organization_events_trace.py
index dc12081142437..38ec570f1e02f 100644
--- a/src/sentry/api/endpoints/organization_events_trace.py
+++ b/src/sentry/api/endpoints/organization_events_trace.py
@@ -1,5 +1,5 @@
 import logging
-from collections import OrderedDict, defaultdict, deque
+from collections import defaultdict, deque
 from typing import (
     TYPE_CHECKING,
     Any,
@@ -561,10 +561,7 @@ def serialize(
         parent_map = self.construct_parent_map(transactions)
         error_map = self.construct_error_map(errors)
         parent_events: Dict[str, TraceEvent] = {}
-        # TODO(3.7): Dictionary ordering in py3.6 is an implementation detail, using an OrderedDict because this way
-        # we try to guarantee in py3.6 that the first item is the root. We can switch back to a normal dict when we're
-        # on python 3.7.
-        results_map: Dict[Optional[str], List[TraceEvent]] = OrderedDict()
+        results_map: Dict[Optional[str], List[TraceEvent]] = defaultdict(list)
         to_check: Deque[SnubaTransaction] = deque()
         # The root of the orphan tree we're currently navigating through
         orphan_root: Optional[SnubaTransaction] = None
@@ -596,11 +593,7 @@ def serialize(
 
                     # Used to avoid removing the orphan from results entirely if we loop
                     orphan_root = current_event
-                    # not using a defaultdict here as a DefaultOrderedDict isn't worth the effort
-                    if parent_span_id in results_map:
-                        results_map[parent_span_id].append(previous_event)
-                    else:
-                        results_map[parent_span_id] = [previous_event]
+                    results_map[parent_span_id].append(previous_event)
                 else:
                     current_event = to_check.popleft()
                     previous_event = parent_events[current_event["id"]]

- Now that we're on py3.8 we know that dictionaries will be ordered,
  which maens we can use the defaultdict and know that order is
  preserved