diff --git a/tiramisu/option.py b/tiramisu/option.py
index 0bc2a98..726b848 100644
--- a/tiramisu/option.py
+++ b/tiramisu/option.py
@@ -51,7 +51,10 @@ class Multi(list):
         self.config = config
         self.opt = opt
         if self.opt.is_master(config):
+            # we pass the list at the list type's init
+            # because a normal init cannot return anything
             super(Multi, self).__init__(lst)
+            # we add the slaves without modifying the master
             for l in lst:
                 try:
                     self.append(l, add_master=False)
@@ -66,7 +69,10 @@ class Multi(list):
 
     def append(self, value, add_master=True):
         """the list value can be updated (appened)
-        only if the option is a master"""
+        only if the option is a master
+        :param add_master: adds slaves without modifiying the master option
+                           if True, adds slaves **and** the master option
+        """
         try:
             master = self.config._cfgimpl_descr.get_master_name()
             if master != self.opt._name: