Let's find the inflection points, we'll need to solve the equation for this
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = 0$$
(the second derivative equals zero),
the roots of this equation will be the inflection points for the specified function graph:
$$\frac{d^{2}}{d x^{2}} f{\left(x \right)} = $$
the second derivative$$\frac{2 \left(\frac{14 \left(7 x - \operatorname{sign}{\left(x \right)}\right) \operatorname{sign}{\left(x \right)}}{7 x^{2} - 2 \left|{x}\right|} - 7 \delta\left(x\right) - \frac{\left(7 \left|{x}\right| - 2\right) \left(\frac{4 \left(7 x - \operatorname{sign}{\left(x \right)}\right)^{2}}{7 x^{2} - 2 \left|{x}\right|} + 2 \delta\left(x\right) - 7\right)}{7 x^{2} - 2 \left|{x}\right|}\right)}{7 x^{2} - 2 \left|{x}\right|} = 0$$
Solve this equationSolutions are not found,
maybe, the function has no inflections