Question: Removing higher order terms in Christoffel symbols

Could anybody give me an idea of how I would go about ignoring the Christoffel symbols with coefficients of order Omega(r)^2 in the following code? Thanks.
 

with(Physics)

[`*`, `.`, Annihilation, AntiCommutator, Antisymmetrize, Assume, Bra, Bracket, Check, Christoffel, Coefficients, Commutator, CompactDisplay, Coordinates, Creation, D_, Dagger, Decompose, Define, Dgamma, Einstein, EnergyMomentum, Expand, ExteriorDerivative, Factor, FeynmanDiagrams, Fundiff, Geodesics, GrassmannParity, Gtaylor, Intc, Inverse, Ket, KillingVectors, KroneckerDelta, LeviCivita, Library, LieBracket, LieDerivative, Normal, Parameters, PerformOnAnticommutativeSystem, Projector, Psigma, Redefine, Ricci, Riemann, Setup, Simplify, SortProducts, SpaceTimeVector, StandardModel, SubstituteTensor, SubstituteTensorIndices, SumOverRepeatedIndices, Symmetrize, TensorArray, Tetrads, ThreePlusOne, ToFieldComponents, ToSuperfields, Trace, TransformCoordinates, Vectors, Weyl, `^`, dAlembertian, d_, diff, g_, gamma_]

(1)

NULL

Setup(metric = -exp(2*alpha(r))*%d_(t)^2+exp(2*beta(r))*%d_(r)^2+r^2*%d_(theta)^2+r^2*sin(theta)^2*(%d_(phi)-Omega(r)*%d_(t))^2)

[metric = {(1, 1) = -exp(2*alpha(r))+(-r^2*cos(theta)^2+r^2)*Omega(r)^2, (1, 4) = -r^2*sin(theta)^2*Omega(r), (2, 2) = exp(2*beta(r)), (3, 3) = r^2, (4, 4) = r^2*sin(theta)^2}]

(2)

g_[]

Physics:-g_[mu, nu] = Matrix(%id = 18446746171579097566)

(3)

Christoffel[nonzero]

Physics:-Christoffel[alpha, mu, nu] = {(1, 1, 2) = -(diff(alpha(r), r))*exp(2*alpha(r))-r*Omega(r)*(cos(theta)-1)*(cos(theta)+1)*(r*(diff(Omega(r), r))+Omega(r)), (1, 1, 3) = r^2*sin(theta)*Omega(r)^2*cos(theta), (1, 2, 1) = -(diff(alpha(r), r))*exp(2*alpha(r))-r*Omega(r)*(cos(theta)-1)*(cos(theta)+1)*(r*(diff(Omega(r), r))+Omega(r)), (1, 2, 4) = -(1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (1, 3, 1) = r^2*sin(theta)*Omega(r)^2*cos(theta), (1, 3, 4) = -r^2*sin(theta)*Omega(r)*cos(theta), (1, 4, 2) = -(1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (1, 4, 3) = -r^2*sin(theta)*Omega(r)*cos(theta), (2, 1, 1) = (diff(alpha(r), r))*exp(2*alpha(r))+r*Omega(r)*(cos(theta)-1)*(cos(theta)+1)*(r*(diff(Omega(r), r))+Omega(r)), (2, 1, 4) = (1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (2, 2, 2) = (diff(beta(r), r))*exp(2*beta(r)), (2, 3, 3) = -r, (2, 4, 1) = (1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (2, 4, 4) = -r*sin(theta)^2, (3, 1, 1) = -r^2*sin(theta)*Omega(r)^2*cos(theta), (3, 1, 4) = r^2*sin(theta)*Omega(r)*cos(theta), (3, 2, 3) = r, (3, 3, 2) = r, (3, 4, 1) = r^2*sin(theta)*Omega(r)*cos(theta), (3, 4, 4) = -r^2*sin(theta)*cos(theta), (4, 1, 2) = -(1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (4, 1, 3) = -r^2*sin(theta)*Omega(r)*cos(theta), (4, 2, 1) = -(1/2)*r*sin(theta)^2*(r*(diff(Omega(r), r))+2*Omega(r)), (4, 2, 4) = r*sin(theta)^2, (4, 3, 1) = -r^2*sin(theta)*Omega(r)*cos(theta), (4, 3, 4) = r^2*sin(theta)*cos(theta), (4, 4, 2) = r*sin(theta)^2, (4, 4, 3) = r^2*sin(theta)*cos(theta)}

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``


 

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