docs: def _make_s_pow_e(self, reac_idx, e_vec):
          """
          Compute s^e in equation 11  (see Ale et al. 2013)
  
          :param reac_idx: the index (that is the column in the stoichiometry matrix)
           of the reaction to consider.
          :type reac_idx: `int`
          :param e_vec: the vector e
          :return: a scalar (s^e)
          """
          return product([self.__stoichoimetry_matrix[i, reac_idx] ** e for i,e in enumerate(e_vec)])