'Returns an iterator of :class:`Call` resources.
:param date after: Only list calls started after this datetime
:param date before: Only list calls started before this datetime'

@normalize_dates
def iter(self, from_=None, ended_after=None, ended_before=None, ended=None, started_before=None, started_after=None, started=None, **kwargs):

    kwargs['from'] = from_
    kwargs['StartTime<'] = started_before
    kwargs['StartTime>'] = started_after
    kwargs['StartTime'] = parse_date(started)
    kwargs['EndTime<'] = ended_before
    kwargs['EndTime>'] = ended_after
    kwargs['EndTime'] = parse_date(ended)
    return super(Calls, self).iter(**kwargs)
