network_los is not available in trip mode choice #1133

network_los is not available in expression files run through expressions.annotate_tables (e.g. trip_mode_choice postprocessor)

Describe the bug

Expression specs evaluated through expressions.compute_columns / expressions.annotate_tables (preprocessors and annotate-table specs) cannot reference network_los. For example, a trip_mode_choice annotate_trips spec that labels trips with their skim time period fails with a NameError, because network_los is not in the locals dictionary used to evaluate the expressions.

compute_columns already exposes skim_dict (and skim_dataset_dict when sharrow is on), but not the Network_LOS object, so helpers such as network_los.skim_time_period_label() and network_los.skim_time_periods cannot be used from these specs unless the calling model happens to add network_los to locals_dict itself. trip_mode_choice does not.

To Reproduce

1. Add the following row to the annotate_trips spec referenced by the annotate_trips setting in trip_mode_choice.yaml (a CSV like trip_mode_choice_annotate_trips_postprocessor.csv):

   Description,Target,Expression
   trip time period label,time_period,network_los.skim_time_period_label(df.depart)
   

   The accompanying network_los.yaml has the usual skim_time_periods block, for example:

   skim_time_periods:
     time_window: 1440
     period_minutes: 30
     periods: [0, 4, 14, 24, 36, 48]
     labels: ["EA", "AM", "MD", "PM", "NI"]

2. Run a model that includes trip_mode_choice (for example the TransLink model, ActivitySim v1.6.0 tag 8ca6741).

3. The run fails at the end of trip_mode_choice, when the annotate-trips spec is evaluated.

Log output:

ERROR: assign_variables - NameError (name 'network_los' is not defined) evaluating: network_los.skim_time_period_label(mid_hour_bin)
Traceback (most recent call last):
  File ".../activitysim/core/assign.py", line 397, in assign_variables
    expr_values = to_series(eval(expression, globals_dict, _locals_dict))
  File "<string>", line 1, in <module>
NameError: name 'network_los' is not defined
ERROR: ===== ERROR IN trip_mode_choice =====
ERROR: name 'network_los' is not defined
Traceback (most recent call last):
  File ".../activitysim/abm/models/trip_mode_choice.py", line 338, in trip_mode_choice
    expressions.annotate_tables(
  File ".../activitysim/core/expressions.py", line 327, in annotate_tables
    results = compute_columns(
  File ".../activitysim/core/expressions.py", line 136, in compute_columns
    results, trace_results, trace_assigned_locals = assign.assign_variables(
NameError: name 'network_los' is not defined

Expected behavior

network_los should be available in every expression evaluated by compute_columns, alongside skim_dict, so a spec can use network_los.skim_time_period_label(...) without each model having to pass network_los explicitly. The time period labels and bounds then come from network_los.yaml, the single place they are defined, and do not have to be duplicated as constants in each spec.

Screenshots

Not applicable.

Additional context

• Workaround without a code change: hard-code the period bounds and labels in the spec, for example pd.cut(df.depart, [0, 4, 14, 24, 36, 48], labels=[...]). This duplicates network_los.yaml and silently goes stale if skim_time_periods changes.
• Other models, such as trip_destination, pass network_los explicitly in their own locals_dict, which is why the same kind of expression works there.