def METHOD_NAME(self):
    r"""
    The Gram matrix that specifies the `\lambda`-brackets of the
    generators.
    EXAMPLES::
        sage: R = lie_conformal_algebras.Weyl(QQbar, ngens=4)
        sage: R.gram_matrix()
        [ 0  0| 1  0]
        [ 0  0| 0  1]
        [-----+-----]
        [-1  0| 0  0]
        [ 0 -1| 0  0]
    """
    return self._gram_matrix