<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def list_file_extensions(path: str, reportevery: int = 1) -> List[str]: """ Returns a sorted list of every file extension found in a directory and its subdirectories. Args: path: path to scan reportevery: report directory progress after every *n* steps Returns: sorted list of every file extension found """

    extensions = set()
    count = 0
    for root, dirs, files in os.walk(path):
        count += 1
        if count % reportevery == 0:
            log.debug("Walking directory {}: {!r}", count, root)
        for file in files:
            filename, ext = os.path.splitext(file)
            extensions.add(ext)
    return sorted(list(extensions))