code: def normalized_external_field(self):
      f = self.log_external_field().T
      f -= np.max(f, 0)
      np.exp(f, f)
      f /= f.sum(0)
      return f.T
  
file_path: nipy/nipy/algorithms/segmentation/segmentation.py
imports: import numpy
  from ._segmentation import _interaction_energy, _ve_step
label_desc: Use image node_id 5 for calling the Segmentation obj's underlying member method code with example usage: obj.normalized_external_field() and returns: f