docs: def omega(k, j, z, x):
          """ omega_k_j """
          sum_out = 0
          for i in range(len(x)):
              sum_in = 0
              for t in range(len(x[i])):
                  sum_in += z[i][k] * EMMMixPLAggregator.indic(j, x[i], t)
              sum_out += sum_in
          return sum_out