 -> Tensor

Computes the :math:`n^{th}` derivative of the digamma function on :attr:`input`.
:math:`n \geq 0` is called the order of the polygamma function.

.. math::
    \psi^{(n)}(x) = \frac{d^{(n)}}{dx^{(n)}} \psi(x)

.. note::
    This function is implemented only for nonnegative integers :math:`n \geq 0`.
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