已知定义域为\(R\)的函数\(y=f\left(x\right) \)满足\(f\left(-x\right)=-f\left(x+4\right) \)，当\(x > 2 \)时，\(f\left(x\right) \)单调递增，若\({x}_{1}+{x}_{2} < 4 \)且\(\left({x}_{1}-2\right)\left({x}_{2}-2\right) < 0 \)，则\(f\left({x}_{1}\right)+f\left({x}_{2}\right) \)的值