def _sample_orthonormal_to(mu):
    """Sample point on sphere orthogonal to mu."""
    v = np.random.randn(mu.shape[0])
    proj_mu_v = mu * np.dot(mu, v) / np.linalg.norm(mu)
    orthto = v - proj_mu_v
    return orthto / np.linalg.norm(orthto)
Sample point on sphere orthogonal to mu.