human
3. Affine decomposition
In order to obtain an affine decomposition, we recast the problem on a fixed, parameter independent, reference domain $\Omega$. We choose one characterized by $\mu_0=\mu_1=\mu_2=\mu_3=\mu_4=1$ and $\mu_5=0$, which we generate through the generate_mesh notebook provided in the data folder."
Please write code following the instructions in jupyter notebook style.
 Give me a code to 3?
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#Here is code to 3.

@PullBackFormsToReferenceDomain()
@AffineShapeParametrization("data/t_bypass_vertices_mapping.vmp")
class Stokes(StokesProblem):

    # Default initialization of members
    def __init__(self, V, **kwargs):
        # Call the standard initialization
        StokesProblem.__init__(self, V, **kwargs)
        # ... and also store FEniCS data structures for assembly
        assert "subdomains" in kwargs
        assert "boundaries" in kwargs
        self.subdomains, self.boundaries = kwargs["subdomains"], kwargs["boundaries"]
        up = TrialFunction(V)
        (self.u, self.p) = split(up)
        vq = TestFunction(V)
        (self.v, self.q) = split(vq)
        self.dx = Measure("dx")(subdomain_data=self.subdomains)
        self.ds = Measure("ds")(subdomain_data=self.boundaries)
        # ... as well as forcing terms and inlet velocity
        self.inlet = Expression(("- 1./0.25*(x[1] - 1)*(2 - x[1])", "0."), degree=2)
        self.f = Constant((0.0, 0.0))
        self.g = Constant(0.0)

    # Return custom problem name
    def name(self):
        return "Stokes2RB"

    # Return the lower bound for inf-sup constant.
    def get_stability_factor_lower_bound(self):
        return 1.

    # Return theta multiplicative terms of the affine expansion of the problem.
    @compute_theta_for_supremizers
    def compute_theta(self, term):
        if term == "a":
            theta_a0 = 1.0
            return (theta_a0, )
        elif term in ("b", "bt"):
            theta_b0 = 1.0
            return (theta_b0, )
        elif term == "f":
            theta_f0 = 1.0
            return (theta_f0, )
        elif term == "g":
            theta_g0 = 1.0
            return (theta_g0, )
        elif term == "dirichlet_bc_u":
            theta_bc0 = 1.
            return (theta_bc0, )
        else:
            raise ValueError("Invalid term for compute_theta().")

    # Return forms resulting from the discretization of the affine expansion of the problem operators.
    @assemble_operator_for_supremizers
    def...