GetServiceDefinitions.
        [Preview API]
        :param str service_type:
        :rtype: [ServiceDefinition]

def get_service_definitions(self, service_type=None):
        """GetServiceDefinitions.
        [Preview API]
        :param str service_type:
        :rtype: [ServiceDefinition]
        """
        route_values = {}
        if service_type is not None:
            route_values['serviceType'] = self._serialize.url('service_type', service_type, 'str')
        response = self._send(http_method='GET',
                              location_id='d810a47d-f4f4-4a62-a03f-fa1860585c4c',
                              version='5.0-preview.1',
                              route_values=route_values)
        return self._deserialize('[ServiceDefinition]', self._unwrap_collection(response))