Keymap: tweak keymap loading type checks

For full keymaps, ensure keymap items are lists to allow predictable
manipulation at runtime.

When calling `keymap_init_from_data` directly, allow any sequence type
to allow tools to define their keymaps as tuples.

release/scripts/modules/bl_keymap_utils/io.py

@@ -227,7 +227,6 @@ def _kmi_props_setattr(kmi_props, attr, value):
 
 
 def keymap_init_from_data(km, km_items, is_modal=False):
-    assert type(km_items) is list
     new_fn = getattr(km.keymap_items, "new_modal" if is_modal else "new")
     for (kmi_idname, kmi_args, kmi_data) in km_items:
         kmi = new_fn(kmi_idname, **kmi_args)
@@ -248,7 +247,14 @@ def keyconfig_init_from_data(kc, keyconfig_data):
     # Runs at load time, keep this fast!
     for (km_name, km_args, km_content) in keyconfig_data:
         km = kc.keymaps.new(km_name, **km_args)
-        keymap_init_from_data(km, km_content["items"], is_modal=km_args.get("modal", False))
+        km_items = km_content["items"]
+        # Check here instead of inside 'keymap_init_from_data'
+        # because we want to allow both tuple & list types in that case.
+        #
+        # For full keymaps, ensure these are always lists to allow for extending them
+        # in a generic way that doesn't have to check for the type each time.
+        assert type(km_items) is list
+        keymap_init_from_data(km, km_items, is_modal=km_args.get("modal", False))
 
 
 def keyconfig_import_from_data(name, keyconfig_data):