code: def _df_simplex(gamma, v, lambda_v, x):
      return -lambda_v * (v - x) - np.sum(gamma * (1 / x), axis=0)
  
file_path: cornac/cornac/models/ctr/ctr.py
imports: import numpy
  from ...utils import get_rng
label_desc: Use image node_id 2 for calling a global function with example usage: _df_simplex(gamma, v, lambda_v, x) and returns: unknown