Construct a new piecewise polynomial representing the antiderivative.
Antiderivative is also the indefinite integral of the function, and derivative is its inverse operation.
nu : ndim-tuple of int
Order of derivatives to evaluate for each dimension. If negative, the derivative is returned.
pp : PPoly
Piecewise polynomial of order k2 = k + n representing the antiderivative of this polynomial.
The antiderivative returned by this function is continuous and continuously differentiable to order n-1, up to floating point rounding error.