-The field type of \p context, as returned by bt_ctf_field_get_type(),
-\em must be equivalent to the field type returned by
-bt_ctf_event_class_get_context_type() for the parent event class
-of \p event.
+If \p context is not \c NULL, the field type of \p context, as returned by
+bt_ctf_field_get_type(), \em must be equivalent to the field type returned by
+bt_ctf_event_class_get_context_type() for the parent class of \p event.