monkey patch chunckedArray gititem

km3io/__init__.py

+import numpy as np
+import awkward as ak
+import awkward1 as ak1
+
 from pkg_resources import get_distribution, DistributionNotFound
 
 version = get_distribution(__name__).version
@@ -5,3 +9,18 @@ version = get_distribution(__name__).version
 from .offline import OfflineReader
 from .online import OnlineReader
 from .gseagen import GSGReader
+
+# to avoid infinite recursion
+old_getitem = ak.ChunkedArray.__getitem__
+
+
+def new_getitem(self, item):
+    """Monkey patch the getitem in awkward.ChunkedArray to apply
+        awkward1.Array masks on awkward.ChunkedArray"""
+    if isinstance(item, (ak1.Array, ak.ChunkedArray)):
+        return ak1.Array(self)[item]
+    else:
+        return old_getitem(self, item)
+
+
+ak.ChunkedArray.__getitem__ = new_getitem