code: def get_fragment_length(data):
      
      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)
docs: lifted from
      https://github.com/pmelsted/pizzly/scripts/pizzly_get_fragment_length.py