Add API docs for constraint module

src/ifcopenshell-python/ifcopenshell/api/constraint/unassign_constraint.py

@@ -18,14 +18,24 @@
 
 
 class Usecase:
-    def __init__(self, file, **settings):
+    def __init__(self, file, product=None, constraint=None):
+        """Unassigns a constraint to a product
+
+        The constraint will not be deleted and is available to be assigned to
+        other products.
+
+        :param product: The product the constraint applies to.
+        :type product: ifcopenshell.entity_instance.entity_instance
+        :param constraint: The IfcObjective constraint
+        :type constraint: ifcopenshell.entity_instance.entity_instance
+        :return: None
+        :rtype: None
+        """
         self.file = file
         self.settings = {
-            "product": None,
-            "constraint": None,
+            "product": product,
+            "constraint": constraint,
         }
-        for key, value in settings.items():
-            self.settings[key] = value
 
     def execute(self):
         for rel in self.settings["product"].HasAssociations: