Added Usecases to assign, edit and unassign Lag Times to the ifcopenshell.api

src/ifcopenshell-python/ifcopenshell/api/sequence/unassign_lag_time.py

@@ -0,0 +1,13 @@
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {
+            "rel_sequence": None,
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        if self.settings["rel_sequence"].TimeLag.LagValue:
+            self.file.remove(self.settings["rel_sequence"].TimeLag.LagValue)
+        self.file.remove(self.settings["rel_sequence"].TimeLag)