ri.Triangulation`
        The triangulation to interpolate over.
    z : (npoints,) array-like
        Array of values, defined at grid points, to interpolate between.
    trifinder : `~matplotlib.tri.TriFinder`, optional
        If this is not specified, the Triangulation's default TriFinder will
        be used by calling `.Triangulation.get_trifinder`.

    Methods
    -------
    `__call__` (x, y) : Returns interpolated values at (x, y) points.
    `gradient` (x, y) : Returns interpolated derivatives at (x, y) points.

    Nc