def _skew_symmetric_cross(a):
 return np.array([[0.0, (- a[2]), a[1]], [a[2], 0.0, (- a[0])], [(- a[1]), a[0], 0.0]])

def _skew_symmetric_cross ( a ) : return np . array ( [ [ 0.0 , ( - a [ 2 ] ) , a [ 1 ] ] , [ a [ 2 ] , 0.0 , ( - a [ 0 ] ) ] , [ ( - a [ 1 ] ) , a [ 0 ] , 0.0 ] ] )
the skew-symmetric cross product of a vector .