from datetime import datetime


def timestamp_microseconds() -> str:
    """
    Return a timestamp in 22-char string format: YYYYMMDD-HHMMSS-microseconds
    """
    now = str(datetime.now().isoformat(sep="T", timespec="microseconds"))
    ts: str = ""
    for i in now:
        if i in ("T", "."):
            ts += "-"
        elif i not in (" ", ":", "-"):
            ts += i
    return ts