Write documentation for sequence API module

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

@@ -20,13 +20,46 @@ import ifcopenshell.api
 
 
 class Usecase:
-    def __init__(self, file, **settings):
+    def __init__(self, file, rel_sequence=None):
+        """Removes any lag time in a sequence
+
+        The schedule is cascaded afterwards.
+
+        :param rel_sequence: The sequence to remove the lag time from.
+        :type rel_sequence: ifcopenshell.entity_instance.entity_instance
+        :return: None
+        :rtype: None
+
+        Example::
+
+            # Let's imagine we are creating a construction schedule. All tasks
+            # need to be part of a work schedule.
+            schedule = ifcopenshell.api.run("sequence.add_work_schedule", model, name="Construction Schedule A")
+
+            # Let's imagine a root construction task
+            construction = ifcopenshell.api.run("sequence.add_task", model,
+                work_schedule=schedule, name="Construction", identification="C")
+
+            # Let's imagine we're building 2 zones, one after another.
+            zone1 = ifcopenshell.api.run("sequence.add_task", model,
+                parent_task=construction, name="Zone 1", identification="C.1")
+            zone2 = ifcopenshell.api.run("sequence.add_task", model,
+                parent_task=construction, name="Zone 2", identification="C.2")
+
+            # Zone 1 finishes, then zone 2 starts.
+            sequence = ifcopenshell.api.run("sequence.assign_sequence", model,
+                relating_process=zone1, related_process=zone2)
+
+            # What if you had to wait 1 week before you could start zone 2?
+            ifcopenshell.api.run("sequence.assign_lag_time", model, rel_sequence=sequence, lag_value="P1W")
+
+            # What if you didn't?
+            ifcopenshell.api.run("sequence.unassign_lag_time", model, rel_sequence=sequence)
+        """
         self.file = file
         self.settings = {
-            "rel_sequence": None,
+            "rel_sequence": rel_sequence,
         }
-        for key, value in settings.items():
-            self.settings[key] = value
 
     def execute(self):
         if len(self.file.get_inverse(self.settings["rel_sequence"].TimeLag)) == 1: