def quaternion_conjugate(quaternion):
    """Return conjugate of quaternion.

    >>> q0 = random_quaternion()
    >>> q1 = quaternion_conjugate(q0)
    >>> q1[0] == q0[0] and all(q1[1:] == -q0[1:])
    True

    """
    q = np.array(quaternion, dtype=np.float64, copy=True)
    np.negative(q[1:], q[1:])
    return q