Remove asserts

Author: gwaramadze

quixstreams/dataframe/windows/time_based.py

@@ -421,8 +421,6 @@ def process_window(
             return [], []
 
         # Look for an existing session that can be extended
-        session_start = None
-        session_end = None
         can_extend_session = False
         existing_aggregated = None
         old_window_to_delete = None
@@ -476,10 +474,6 @@ def process_window(
 
             aggregated = self._aggregate_value(current_value, value, timestamp_ms)
 
-        # By this point, session_start and session_end are guaranteed to be set
-        assert session_start is not None  # noqa: S101
-        assert session_end is not None  # noqa: S101
-
         # Output intermediate results for aggregations
         if aggregate:
             updated_windows.append(