def METHOD_NAME(self, inlet_state):
    time = self.flowsheet().time
    p = next(iter(self.config.property_package.phase_list))
    def beta_rule(b, t):
        # We know that we are constructing this property package with a
        # single phase, but we use heat_capacity_ratio_phase nonetheless
        # for compatibility with "generic" property packages.
        gamma = inlet_state[t].heat_capacity_ratio_phase[p]
        return b.beta[t] == (gamma - 1.0) / gamma
    self.beta_eqn = Constraint(time, rule=beta_rule)