<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def to_microseconds(value):
 """Convert a datetime to microseconds since the unix epoch. Args: value (datetime.datetime):
 The datetime to covert. Returns: int: Microseconds since the unix epoch. """

    if not value.tzinfo:
        value = value.replace(tzinfo=pytz.utc)
    # Regardless of what timezone is on the value, convert it to UTC.
    value = value.astimezone(pytz.utc)
    # Convert the datetime to a microsecond timestamp.
    return int(calendar.timegm(value.timetuple()) * 1e6) + value.microsecond