WIP refactoring representations to be incrementally edited. See #1222.

# Conflicts:
#	src/ifcblenderexport/blenderbim/bim/operator.py

src/ifcopenshell-python/ifcopenshell/util/element.py

@@ -93,3 +93,32 @@ def replace_attribute(element, old, new):
                 if item == old:
                     new_attribute[j] = new
                     element[i] = new_attribute
+
+
+def is_representation_of_context(representation, context, subcontext=None, target_view=None):
+    if target_view is not None:
+        return (
+            representation.ContextOfItems.is_a("IfcGeometricRepresentationSubContext")
+            and representation.ContextOfItems.TargetView == target_view
+            and representation.ContextOfItems.ContextIdentifier == subcontext
+            and representation.ContextOfItems.ContextType == context
+        )
+    elif subcontext is not None:
+        return (
+            representation.ContextOfItems.is_a("IfcGeometricRepresentationSubContext")
+            and representation.ContextOfItems.ContextIdentifier == subcontext
+            and representation.ContextOfItems.ContextType == context
+        )
+    elif representation.ContextOfItems.ContextType == context:
+        return True
+
+
+def get_representation(element, context, subcontext=None, target_view=None):
+    if element.is_a("IfcProduct") and element.Representation:
+        for r in element.Representation.Representations:
+            if is_representation_of_context(r, context, subcontext, target_view):
+                return r
+    elif element.is_a("IfcTypeProduct") and element.RepresentationMaps:
+        for r in element.RepresentationMaps:
+            if is_representation_of_context(r.MappedRepresentation, context, subcontext, target_view):
+                return r.MappedRepresentation