purge cost schedules

src/ifcopenshell-python/ifcopenshell/api/cost/remove_cost_schedule.py

@@ -16,6 +16,8 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+import ifcopenshell.api
+
 
 class Usecase:
     def __init__(self, file, cost_schedule=None):
@@ -42,4 +44,13 @@ class Usecase:
 
     def execute(self):
         # TODO: do a deep purge
+        for inverse in self.file.get_inverse(self.settings["cost_schedule"]):
+            if inverse.is_a("IfcRelAssignsToControl"):
+                [
+                    ifcopenshell.api.run(
+                        "sequence.remove_cost_item", self.file, task=related_object
+                    )
+                    for related_object in inverse.RelatedObjects
+                    if related_object.is_a("IfcCostItem")
+                ]
         self.file.remove(self.settings["cost_schedule"])