def METHOD_NAME(self, arr):
    """Get the approximate coefficients at a given level."""
    new = []
    if len(arr) == 1:
        return [arr[0]]
    for x in range(math.floor(len(arr) / 2)):
        new.append((arr[2 * x] + arr[2 * x + 1]) / math.sqrt(2))
    return new