SFTP Sensor Airflow 1.9.0

sftp_sensor.py

# -*- coding: utf-8 -*-
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from airflow.contrib.hooks.ssh_hook import SSHHook
from airflow.operators.sensors import BaseSensorOperator
from airflow.utils.decorators import apply_defaults


class SFTPSensor(BaseSensorOperator):
    """
    Waits for a file or directory to be present on SFTP usign SSH Hook
    :param path: Remote file or directory path
    :type path: str
    :param ssh_conn_id: The connection to run the sensor against
    :type ssh_conn_id: str
    """
    template_fields = ('path',)
    ui_color = '#89a203'
    
    @apply_defaults
    def __init__(self, path, ssh_conn_id='ssh_default', success_when_file_exists=True, *args, **kwargs):
        super(SFTPSensor, self).__init__(*args, **kwargs)

        self.path = path
        self.success_when_file_exists = success_when_file_exists
        self.ssh_conn_id = ssh_conn_id
        self.file_exists = None

    def _create_hook(self):
        """Return connection hook."""
        return SSHHook(ssh_conn_id=self.ssh_conn_id)

    def poke(self, context):
        with self._create_hook().get_conn() as ssh_client:
            sftp_client = ssh_client.open_sftp()
            self.log.info('Poking for %s', self.path)
            self.log.info('success_when_file_exists : %s', self.success_when_file_exists)
            try:
                sftp_client.stat(self.path)
                self.log.info('File exists.')
                self.file_exists = True
            except IOError:
                self.file_exists = False
                self.log.info('File does not exists.')
            except Exception as e:
                self.log.error(e)

        if self.file_exists == None:
            raise Exception('Error checking file.')
        
        return self.file_exists == self.success_when_file_exists

Hi, how do I implement this code to my dag? I'm unsure where to start