Write documentation for resource API module

src/ifcopenshell-python/ifcopenshell/api/resource/calculate_resource_work.py

@@ -23,11 +23,40 @@ import ifcopenshell.util.element
 
 
 class Usecase:
-    def __init__(self, file, **settings):
+    def __init__(self, file, resource=None):
+        """Calculates the work that a resource is used for
+
+        This is an unofficial parametric calculation that may be done on a
+        resource based on careful analysis of the relationships between the
+        costing, scheduling, and resource domains in IFC.
+
+        A resource may store a productivity rate in a property set called
+        EPset_Productivity. This stores three properties:
+
+        * BaseQuantityConsumed - a duration that the resource is consumed for.
+        * BaseQuantityProducedName - what quantity the resource can produce,
+            such as area or volume.
+        * BaseQuantityProducedValue - what value of that quantity the resource
+            can produce during that duration.
+
+        For example, a labour or equipment resource might produce 100m3 of
+        NetVolume every day (i.e. 8 hours are consumed).
+
+        Then, if a resource is assigned to a construction task, and that
+        construction task is assigned to concrete slabs totalling 200m3, we can
+        calculate that the resource consumes 16 hours of work.
+
+        This calculated work is stored against the resource as scheduled work
+        under the resource time data.
+
+        :param resource: The IfcConstructionResource that you want to calculate
+            the work performed.
+        :type resource: ifcopenshell.entity_instance.entity_instance
+        :return None:
+        :rtype None:
+        """
         self.file = file
-        self.settings = {"resource": None}
-        for key, value in settings.items():
-            self.settings[key] = value
+        self.settings = {"resource": resource}
 
     def execute(self):
         self.productivity = ifcopenshell.util.element.get_psets(