stress energt lorentz boost

import sympy
sympy.init_printing()
g = sympy.Symbol('gamma')
b = sympy.Symbol('beta')
T00 = sympy.Symbol('T^{0 0}')
Txx = sympy.Symbol('T^{x x}')
T0x = sympy.Symbol('T^{0 x}')
boost = sympy.Matrix([[g,g*b],[g*b,g]])
stress_energy = sympy.Matrix([[T00,T0x],[T0x,Txx]])
temp = boost*stress_energy*boost
temp[0,1].subs(b,-b).simplify()