Get distance matrix given a matrix. Used in testing.

def get_distance_matrix(x):
    """Get distance matrix given a matrix. Used in testing."""
    square = nd.sum(x ** 2.0, axis=1, keepdims=True)
    distance_square = square + square.transpose() - (2.0 * nd.dot(x, x.transpose()))
    return nd.sqrt(distance_square)