You can now assign task successor and predecessors. Sweet. Thanks myoualid!

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

@@ -0,0 +1,18 @@
+import ifcopenshell
+import ifcopenshell.api
+
+
+class Usecase:
+    def __init__(self, file, **settings):
+        self.file = file
+        self.settings = {
+            "relating_process": None,
+            "related_process": None,
+        }
+        for key, value in settings.items():
+            self.settings[key] = value
+
+    def execute(self):
+        for rel in self.settings["related_process"].IsSuccessorFrom or []:
+            if rel.RelatingProcess == self.settings["relating_process"]:
+                self.file.remove(rel)