code: def norm_l1_tf(Z, phi, n_orient, w_time):
      """L1 norm for TF."""
      if Z.shape[0]:
          n_positions = Z.shape[0] // n_orient
          Z_ = np.sqrt(
              np.sum(
                  (np.abs(Z) ** 2.0).reshape((n_orient, -1), order="F"),
                  axis=0,
              )
          )
          Z_ = Z_.reshape((n_positions, -1), order="F")
          if w_time is not None:
              Z_ *= w_time
          l1_norm = phi.norm(Z_, ord=1).sum()
      else:
          l1_norm = 0.0
      return l1_norm
  
imports: import functools
  from math import sqrt
  import numpy
  from ..time_frequency._stft import istft, stft, stft_norm1, stft_norm2
  from ..utils import _check_option, _get_blas_funcs, _validate_type, logger, sum_squared, verbose, warn
  from .mxne_debiasing import compute_bias
label_desc: Use image node_id 16 for calling a global function with example usage: norm_l1_tf(Z, phi, n_orient, w_time) and returns: l1_norm