def tril_indices_from(arr,k=0):
    if not arr.ndim==2 and arr.shape[0] == arr.shape[1]:
        raise ValueError("input array must be 2-d and square")
    return tril_indices(arr.shape[0],k)
Return the indices for the lower-triangle of an (n, n) array.
dataset/ETHPy150Open nipy/nitime/nitime/index_utils.py/tril_indices_from