Find the Taylor series in $(x-a)$ through $(x-a)^{3}$ for $$f(x) = \tan x, \quad a = \dfrac{\pi}{4}$$

$f(x) =$ $+$ $\left(x-\frac{\pi}{4}\right) +$ $\left(x-\frac{\pi}{4}\right)^{2} +$ $\left(x-\frac{\pi}{4}\right)^{3} + O\left(\left(x-\frac{\pi}{4}\right)^{4}\right)$.