<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def parse_api_datetime(value):
 """ parse a datetime returned from the salesforce API. in python 3 we should just use a strptime %z, but until then we're just going to assert that its a fixed offset of +0000 since thats the observed behavior. getting python 2 to support fixed offset parsing is too complicated for what we need imo."""

    dt = datetime.strptime(value[0:DATETIME_LEN], API_DATE_FORMAT)
    offset_str = value[DATETIME_LEN:]
    assert offset_str in ["+0000", "Z"], "The Salesforce API returned a weird timezone."
    return dt