Convert a timestamp string into a microseconds value
    :param timestamp
    :return time in microseconds

def timestamp_to_microseconds(timestamp):
    """Convert a timestamp string into a microseconds value
    :param timestamp
    :return time in microseconds
    """
    timestamp_str = datetime.datetime.strptime(timestamp, ISO_DATETIME_REGEX)
    epoch_time_secs = calendar.timegm(timestamp_str.timetuple())
    epoch_time_mus = epoch_time_secs * 1e6 + timestamp_str.microsecond
    return epoch_time_mus