like, compatible objects
    The two dimensional series is evaluated at the points in the
    Cartesian product of `x` and `y`.  If `x` or `y` 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
--------
polyval, polyval2d, polyval3d, polygrid3d

Examples
--------
>>> from numpy.polynomial import polynomial as P
>>> c = ((1, 2, 3), (4, 5, 6))
>>> P.polygrid2d([0, 1], [0, 1], c)
array([[ 1.,  6.],
       [ 5., 21.]])

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