diff --git a/deeprank/generate/DataGenerator.py b/deeprank/generate/DataGenerator.py
index f4596cf2..6de5bb67 100644
--- a/deeprank/generate/DataGenerator.py
+++ b/deeprank/generate/DataGenerator.py
@@ -48,6 +48,7 @@ def __init__(self, pdb_select=None, pdb_source=None,
             pssm_source (list(str), optional): List of folders where to find the PSSM files
             align (dict, optional): Dicitionary to align the compexes, 
                                     e.g. align = {"selection":{"chainID":["A","B"]},"axis":"z"}}
+                                    e.g. align = {"selection":"interface","plane":"xy"}
                                     if "selection" is not specified the entire complex is used for alignement
             compute_targets (list(str), optional): List of python files computing the targets,
                 "pdb_native" must be set if having targets to compute.