No `inputs/` directory is referenced as existing; the task is self-contained. Here is the solution.

def merge_intervals(intervals):
    if not intervals:
        return []
    ordered = sorted(intervals, key=lambda iv: (iv[0], iv[1]))
    merged = []
    for start, end in ordered:
        if merged and start <= merged[-1][1]:
            if end > merged[-1][1]:
                merged[-1][1] = end
        else:
            merged.append([start, end])
    return merged