Instantiate ExportRequest
        :param cfg: request configuration, should consist of request description (url and optional parameters)
        :param login:
        :param pswd:
        :param request_type: TYPE_SET_FIELD_VALUE || TYPE_CREATE_ENTITY || TYPE_DELETE_ENTITY || TYPE_CREATE_RELATION
        :return: ExportRequest instance

def factory(cfg, login, pswd, request_type):
        """
        Instantiate ExportRequest
        :param cfg: request configuration, should consist of request description (url and optional parameters)
        :param login:
        :param pswd:
        :param request_type: TYPE_SET_FIELD_VALUE || TYPE_CREATE_ENTITY || TYPE_DELETE_ENTITY || TYPE_CREATE_RELATION
        :return: ExportRequest instance
        """
        if request_type == ExportRequest.TYPE_SET_FIELD_VALUE:
            return SetFieldValueRequest(cfg, login, pswd)
        elif request_type == ExportRequest.TYPE_CREATE_ENTITY:
            return CreateEntityRequest(cfg, login, pswd)
        elif request_type == ExportRequest.TYPE_DELETE_ENTITY:
            return DeleteEntityRequest(cfg, login, pswd)
        elif request_type == ExportRequest.TYPE_CREATE_RELATION:
            return CreateRelationRequest(cfg, login, pswd)
        else:
            raise NotImplementedError('Not supported request type - {}'.format(request_type))