def METHOD_NAME(self, p, n):
    """ 
    Neuman  boundary condition
    Parameters
    ----------
    p: (NQ, NE, 2)
    n: (NE, 2)
    grad*n : (NQ, NE, 2)
    """
    grad = self.gradient(p) # (NQ, NE, 2)
    val = np.sum(grad*n, axis=-1) # (NQ, NE)
    return val