Return the saved feature indexes that will be concatenated
    Inputs:
        sfs (list): saved features by hook function, in other words intermediate activations
        last (bool): whether to concatenate only last different activation, or all from the encoder model

def get_sfs_idxs(sfs, last=True):
    """
    Return the saved feature indexes that will be concatenated
    Inputs:
        sfs (list): saved features by hook function, in other words intermediate activations
        last (bool): whether to concatenate only last different activation, or all from the encoder model
    """
    if last:
        feature_szs = [sfs_feats.features.size()[-1] for sfs_feats in sfs]
        sfs_idxs = list(np.where(np.array(feature_szs[:-1]) != np.array(feature_szs[1:]))[0])
        if feature_szs[0] != feature_szs[1]: sfs_idxs = [0] + sfs_idxs
    else: sfs_idxs = list(range(len(sfs)))
    return sfs_idxs