class_docstr: Works with _WeakArgsDict to provide a weak cache for function args.
  When any of those args are gc'd, the pair is removed from the cache.
class_docstr_tok: ["Works","with","_WeakArgsDict","to","provide","a","weak","cache","for","function","args",".","When","any","of","those","args","are","gc","'d",",","the","pair","is","removed","from","the","cache","."]
code: def __len__(self):
      return len(self._items)
  
imports: from collections import OrderedDict, Sequence
  from itertools import compress
  from weakref import WeakKeyDictionary, ref
  from six.moves._thread import allocate_lock
  from toolz.sandbox import unzip
  from trading_calendars.utils.memoize import lazyval
  from zipline.utils.compat import wraps
label_desc: Use image node_id 3 for calling the _WeakArgs obj's underlying member method code with example usage: obj.__len__() and returns: len