@property
    def nfree(self):
        return self['nfree']
rebuild a mutable tree from the stack
dataset/ETHPy150Open mne-tools/mne-python/mne/cov.py/Covariance.nfree--crossover with--dataset/ETHPy150Open NervanaSystems/neon/neon/backends/float_ew.py/_build_tree