def METHOD_NAME(self, station_id, request_dt_time, number_results=5):
    self.headers = {
        'authorization': self.open_trans_api_key,
        'content-type': 'application/xml; charset=utf-8',
        'accept-charset': 'utf-8'
    }
    self.xml_data = u"""
                <?xml version="1.0" encoding="UTF-8"?>
                <Trias version="1.1" xmlns="http://www.vdv.de/trias" xmlns:siri="http://www.siri.org.uk/siri" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
                    <ServiceRequest>
                        <siri:RequestTimestamp>%s</siri:RequestTimestamp>
                        <siri:RequestorRef>EPSa</siri:RequestorRef>
                        <RequestPayload>
                            <StopEventRequest>
                                <Location>
                                    <LocationRef>
                                        <StopPointRef>%s</StopPointRef>
                                    </LocationRef>
                                    <DepArrTime>%s</DepArrTime>
                                </Location>
                                <Params>
                                    <NumberOfResults>%s</NumberOfResults>
                                    <StopEventType>departure</StopEventType>
                                    <IncludePreviousCalls>false</IncludePreviousCalls>
                                    <IncludeOnwardCalls>true</IncludeOnwardCalls>
                                    <IncludeRealtimeData>true</IncludeRealtimeData>
                                </Params>
                            </StopEventRequest>
                        </RequestPayload>
                    </ServiceRequest>
                </Trias>
                """ % (str(request_dt_time), str(station_id), str(request_dt_time), str(number_results))
    self.r = requests.post(self.url, self.xml_data, headers=self.headers, timeout=5)
    if (self.r.status_code == 429):
        raise OpenTransRateLimitException("The rate limit of OpenTransportdata has exceeded")
    if (self.r.status_code != requests.codes.ok):
        self.r.raise_for_status()
    self.r.encoding = 'utf-8'  # TODO better encoding solution
    return self.r.text.encode('utf-8')