input: Write a python function to send a POST request to the '/web_service' endpoint of the provided Flask application and handle the JSON response.
  assert send_post_request('http://127.0.0.1:5000/web_service', {'input_key': 'input_value'}) == {'key1': 'val1', 'key2': 'val2'}
  assert send_post_request('http://127.0.0.1:5000/web_service', {'another_key': 'another_value'}) == {'key1': 'val1', 'key2': 'val2'}
output: import requests
  
  def send_post_request(url, payload):
      response = requests.post(url, json=payload)
      return response.json()