class_docstr: Nested Conditional Logit (RUNMNL), data handling test
  
  unfinished, does not do anything yet
code: def loglike_leafbranch(self, params, tau):
      # normalization ?
      # check/change naming for tau
      xb = self.xbetas(params)
      expxb = np.exp(xb / tau)
      sumexpxb = expxb.sum(1)  # [:,None]
      logsumexpxb = np.log(sumexpxb)
      # loglike = (self.endog * xb).sum(1) - logsumexpxb
      probs = expxb / sumexpxb[:, None]
      return probs, logsumexpxp
  
file_path: statsmodels/statsmodels/sandbox/regression/runmnl.py
imports: import numpy
  import numpy.lib.recfunctions
  from scipy import optimize
label_desc: Use image node_id 3 for calling the TryNCLogit obj's underlying member method code with example usage: obj.loglike_leafbranch(params, tau) and returns: probs,  logsumexpxp