def nonel_rxn_rate(x):
    """
        Returns the reaction rate, f, for each specie (listed in x)
        through one or multiple (number of columns in stoich_r)
        nonelementary reactions.

        f = sum(omega_j*nu_ij) for i species in j reactions.

        INPUTS
        ======
        x:        numeric list or array
                  concentrations of reactants

        RETURNS
        =======
        f:        the reaction rate for each specie, numeric
        """
    raise NotImplementedError
