make _default_ignore immutable
@@ -163,8 +163,8 @@ class BIDSLayout(object):
indexing will be faster).
"""
- _default_ignore = ["code", "stimuli", "sourcedata", "models",
- re.compile(r'^\.')]
+ _default_ignore = ("code", "stimuli", "sourcedata", "models",
+ re.compile(r'^\.'))
def __init__(self, root, validate=True, absolute_paths=True,
derivatives=False, config=None, sources=None, ignore=None,
