`y` in the second, and `z` in
the third.

The parameters `x`, `y`, and `z` are converted to arrays only if they
are tuples or a lists, otherwise they are treated as a scalars. In
either case, either `x`, `y`, and `z` or their elements must support
multiplication and addition both with themselves and with the elements
of `c`.

If `c` has fewer than three dimensions, ones are implicitly appended to
its shape to make it 3-D. The shape of the result will be c.shape[3:] +
x.shape + y.shape + z.shape.

Parameters
----------
x, y, z : array_like, compatible objects
    The three dimensional series is evaluated at the points in the
    Cartesian product of `x`, `y`, and `z`.  If `x`, `y`, or `z` is a
    list or tuple, it is first converted to an ndarray, otherwise it is
    left unchanged and, if it isn't an ndarray, it is treated as a
    scalar.
c : array_like
    Array of coefficients ordered so that the coefficients for terms of
    degree i,j are contained in ``c[i,j]``. If `c` has dimension
    greater than two the remaining indices enumerate multiple sets of
    coefficients.

Returns
-------
values : ndarray, compatible object
    The values of the two dimensional polynomial at points in the Cartesian
    product of `x` and `y`.

See Also
--------
chebval, chebval2d, chebgrid2d, chebval3d
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