code: def mean_grad(x, beta):
      """gradient/Jacobian for d (x*beta)/ d beta"""
      return x
  
file_path: statsmodels/statsmodels/sandbox/regression/tools.py
imports: import numpy
  from scipy import special
  from scipy.special import gammaln
label_desc: Use image node_id 3 for calling a global function with example usage: mean_grad(x, beta) and returns: x