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

def antiderivative(self, nu):

    p = self.construct_fast(self.c.copy(), self.x, self.extrapolate)
    for (axis, n) in enumerate(nu):
        p._antiderivative_inplace(n, axis)
    p._ensure_c_contiguous()
    return p
