Add documentation for cost module

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

@@ -22,11 +22,37 @@ from datetime import datetime
 
 
 class Usecase:
-    def __init__(self, file, **settings):
+    def __init__(self, file, name=None, predefined_type="NOTDEFINED"):
+        """Add a new cost schedule
+
+        A cost schedule is a group of cost items which typically represent a
+        cost plan or breakdown of the project. This may be used as an estimate,
+        bid, or actual cost.
+
+        Alternatively, a cost schedule may also represent a schedule of rates,
+        which include cost items which capture unit rates for different elements
+        or processes.
+
+        As such, creating a cost schedule is necessary prior to creating and
+        managing any cost items.
+
+        :param name: The name of the cost schedule.
+        :type name: str, optional
+        :param predefined_type: The predefined type of the cost schedule, chosen
+            from a valid type in the IFC documentation for
+            IfcCostScheduleTypeEnum
+        :type predefined_type: str, optional
+        :return: The newly created IfcCostSchedule entity
+        :rtype: ifcopenshell.entity_instance.entity_instance
+
+        Example::
+
+            schedule = ifcopenshell.api.run("cost.add_cost_schedule", model)
+            # Now that we have a cost schedule, we may add cost items to it
+            item = ifcopenshell.api.run("cost.add_cost_item", model, cost_schedule=schedule)
+        """
         self.file = file
-        self.settings = {"name": None, "predefined_type": "NOTDEFINED", "start_time": datetime.now()}
-        for key, value in settings.items():
-            self.settings[key] = value
+        self.settings = {"name": name, "predefined_type": predefined_type}
 
     def execute(self):
         cost_schedule = ifcopenshell.api.run(