lifted from
    https://github.com/pmelsted/pizzly/scripts/pizzly_get_fragment_length.py

def get_fragment_length(data):
    """
    lifted from
    https://github.com/pmelsted/pizzly/scripts/pizzly_get_fragment_length.py
    """
    h5 = kallisto.get_kallisto_h5(data)
    cutoff = 0.95
    with h5py.File(h5) as f:
        x = np.asarray(f['aux']['fld'], dtype='float64')
    y = np.cumsum(x)/np.sum(x)
    fraglen = np.argmax(y > cutoff)
    return(fraglen)