Refactor model updating into single function call

src/lcm/input_processing/process_model.py

@@ -37,9 +37,7 @@ def process_model(model: Model) -> InternalModel:
         The processed model.
 
     """
-    discrete_vars_to_update = _get_discrete_vars_with_non_index_options(model)
-    if discrete_vars_to_update:
-        model = _get_model_with_only_index_options(model, discrete_vars_to_update)
+    model = _convert_discrete_options_to_indices(model)
 
     params = create_params_template(model)
 
@@ -246,29 +244,28 @@ def weight_func(*args, **kwargs):
     return weight_func
 
 
-def _get_discrete_vars_with_non_index_options(model: Model) -> list[str]:
-    gridspecs = get_gridspecs(model)
-    discrete_vars = []
-    for name, spec in gridspecs.items():
-        if isinstance(spec, DiscreteGrid) and list(spec.options) != list(
-            range(len(spec.options))
-        ):
-            discrete_vars.append(name)
-    return discrete_vars
+def _convert_discrete_options_to_indices(model: Model) -> Model:
+    """Update the user model to ensure that discrete variables have index options.
 
+    Args:
+        model: The model as provided by the user.
 
-def _get_model_with_only_index_options(
-    model: Model,
-    discrete_vars_to_update: list[str],
-) -> Model:
-    """Update the user model to ensure that discrete variables have index options."""
+    Returns:
+        The model with all discrete variables having index options.
+
+    """
     gridspecs = get_gridspecs(model)
 
+    non_index_discrete_vars = _get_discrete_vars_with_non_index_options(model)
+
+    if not non_index_discrete_vars:
+        return model
+
     functions = model.functions.copy()
     states = model.states.copy()
     choices = model.choices.copy()
 
-    for var in discrete_vars_to_update:
+    for var in non_index_discrete_vars:
         grid = gridspecs[var]
         if isinstance(grid, DiscreteGrid):
             index_grid = DiscreteGrid(options=list(range(len(grid.options))))
@@ -289,6 +286,17 @@ def _get_model_with_only_index_options(
     )
 
 
+def _get_discrete_vars_with_non_index_options(model: Model) -> list[str]:
+    gridspecs = get_gridspecs(model)
+    discrete_vars = []
+    for name, spec in gridspecs.items():
+        if isinstance(spec, DiscreteGrid) and list(spec.options) != list(
+            range(len(spec.options))
+        ):
+            discrete_vars.append(name)
+    return discrete_vars
+
+
 def _get_index_to_label_func(labels_array, name):
     arg_name = f"__{name}_index__"