fix: add model reference when converting from feature to frame

Author: lachlangrose

.gitignore

@@ -135,4 +135,5 @@ docs/source/sg_execution_times.rst
 conda/index.html
 conda/channeldata.json
 conda/noarch
-conda/win-64
+conda/win-64
+.DS_Store

LoopStructural/modelling/features/_feature_converters.py

@@ -1,6 +1,9 @@
-from LoopStructural.modelling.features.fold import FoldEvent
+from LoopStructural.modelling.features.fold import FoldEvent, FoldFrame
 from LoopStructural.modelling.features.builders import FoldedFeatureBuilder, StructuralFrameBuilder
 def add_fold_to_feature(feature, fold_frame,**kwargs):
+    if not isinstance(fold_frame, FoldFrame):
+        raise ValueError("fold_frame must be a FoldFrame instance")
+        
     fold = FoldEvent(fold_frame, name=f"Fold_{feature.name}", invert_norm=kwargs.get('invert_fold_norm', False))
 
     builder = FoldedFeatureBuilder.from_feature_builder(

LoopStructural/modelling/features/builders/_structural_frame_builder.py

@@ -148,6 +148,7 @@ def from_feature_builder(cls, feature_builder, **kwargs):
             bounding_box=feature_builder.model.bounding_box,
             nelements=[feature_builder.interpolator.n_elements]*3,
             name=feature_builder.name,
+            model=feature_builder.model,
             **kwargs
         )
         builder.add_data_from_data_frame(feature_builder.data)

LoopStructural/modelling/features/fold/_foldframe.py

@@ -19,7 +19,24 @@ def __init__(self, name, features, fold=None, model=None):
         features
         """
         super().__init__(name, features, fold, model)
+    @classmethod
+    def from_structural_frame(cls, frame, fold=None):
+        """
+        Create a FoldFrame from an existing StructuralFrame
+
+        Parameters
+        ----------
+        frame - StructuralFrame
+            the structural frame to convert to a fold frame
+        fold - FoldEvent, optional
+            the fold event to associate with the fold frame
 
+        Returns
+        -------
+        FoldFrame
+            the new fold frame
+        """
+        return cls(frame.name, frame.features, fold, frame.model)
     def calculate_fold_axis_rotation(self, feature_builder, fold_axis=None):
         """
         Calculate the fold axis rotation angle by finding the angle between the