Add docs to layer API

src/ifcopenshell-python/ifcopenshell/api/layer/edit_layer.py

@@ -18,11 +18,27 @@
 
 
 class Usecase:
-    def __init__(self, file, **settings):
+    def __init__(self, file, layer=None, attributes=None):
+        """Edits the attributes of an IfcPresentationLayerAssignment
+
+        For more information about the attributes and data types of an
+        IfcPresentationLayerAssignment, consult the IFC documentation.
+
+        :param layer: The IfcPresentationLayerAssignment entity you want to edit
+        :type layer: ifcopenshell.entity_instance.entity_instance
+        :param attributes: a dictionary of attribute names and values.
+        :type attributes: dict, optional
+        :return: None
+        :rtype: None
+
+        Example::
+
+            layer = ifcopenshell.api.run("layer.add_layer", model, Name="AI-WALL")
+            ifcopenshell.api.run("layer.edit_layer", model,
+                layer=layer, attributes={"Description": "All walls, based on the AIA standard."})
+        """
         self.file = file
-        self.settings = {"layer": None, "attributes": {}}
-        for key, value in settings.items():
-            self.settings[key] = value
+        self.settings = {"layer": layer, "attributes": attributes or {}}
 
     def execute(self):
         for name, value in self.settings["attributes"].items():