A proof of the Biswas–Mitra–Bhattacharyya conjecture for the ideal quantum gas trapped under the generic power law potential $U=\sum\nolimits_{i=1}^{d}{{c}_{i}}\left\vert \frac{{{x}_{i}}}{{{a}_{i}}}\right\vert^{{{n}_{i}}}$ inddimensions