Piecewise polynomial curve specified by points and derivatives
This class represents a curve that is a piecewise polynomial. It passes through a list of points and has specified derivatives at each point. The degree of the polynomial may vary from segment to segment, as may the number of derivatives available. The degree should not exceed about thirty.
Appending points to the end of the curve is efficient.
Parameters :  xi : arraylike
yi : arraylike or list of arraylikes
orders : list of integers, or integer
direction : {None, 1, 1}
axis : int, optional


Notes
If orders is None, or orders[i] is None, then the degree of the polynomial segment is exactly the degree required to match all i available derivatives at both endpoints. If orders[i] is not None, then some derivatives will be ignored. The code will try to use an equal number of derivatives from each end; if the total number of derivatives needed is odd, it will prefer the rightmost endpoint. If not enough derivatives are available, an exception is raised.
Methods
__call__(x)  Evaluate the interpolant 
append(xi, yi[, order])  Append a single point with derivatives to the PiecewisePolynomial 
derivative(x[, der])  Evaluate one derivative of the polynomial at the point x 
derivatives(x[, der])  Evaluate many derivatives of the polynomial at the point x 
extend(xi, yi[, orders])  Extend the PiecewisePolynomial by a list of points 