Inclined asymptote can be found by calculating the limit of Piecewise((x, 0 = 1), (1, 1 = 1), (0, True)), divided by x at x->+oo and x ->-oo
$$\lim_{x \to -\infty}\left(\frac{\begin{cases} x & \text{for}\: 0 = 1 \\1 & \text{for}\: 1 = 1 \\0 & \text{otherwise} \end{cases}}{x}\right) = 0$$
Let's take the limitso,
inclined coincides with the horizontal asymptote on the right
$$\lim_{x \to \infty}\left(\frac{\begin{cases} x & \text{for}\: 0 = 1 \\1 & \text{for}\: 1 = 1 \\0 & \text{otherwise} \end{cases}}{x}\right) = 0$$
Let's take the limitso,
inclined coincides with the horizontal asymptote on the left