import numpy.linalg as la
def svd_truncate_with_singular_values(ttslice,center,svs,cutoff=None,chi_max=None,chi_min=None):
    pass
def svd_truncate(ttslice,center,cutoff=None,chi_max=None,chi_min=None,svd=la.svd):
    pass

def var_truncate(ttslice,chi=None):
    pass
