Python key error in Lambda function

This is my first lambda function but the python code should be correct yet I am getting an error. Python code:

import json
import boto3

def get_volume_id_from_arn(volume_arn):
    #Split the ARN using the colon (':') separator
    arn_parts = volume_arn.split(':')
    #The Volume ID is the last part of the ARN after the 'volume/' prefix
    volume_id = arn_parts[-1].split('/')[-1]
    return volume_id

def lambda_handler(event, context):
    print(event)
    #Grab the event and look for resources
    #Grab the first resource line
    volume_arn = event['resources'][0]

    #Call get_volume_id_from_arn and pass it the arn for conversion
    volume_id = get_volume_id_from_arn(volume_arn)
    #Create an ec2 client for boto3
    ec2_client = boto3.client('ec2')
    #Use boto3 to call the modify_volume function to convert the volume to gp3
    responce = client.modify_volume(
        VolumeId=volume_id,
        VolumeType='gp3'
    )

When I deploy and test I get this result:

Response
{
  "errorMessage": "'resources'",
  "errorType": "KeyError",
  "requestId": "3d116529-e903-4b49-9014-c00a5d23a7ca",
  "stackTrace": [
    "  File \"/var/task/lambda_function.py\", line 16, in lambda_handler\n    volume_arn = event['resources'][0]\n"
  ]
}

Function Logs
START RequestId: 3d116529-e903-4b49-9014-c00a5d23a7ca Version: $LATEST
{'key1': 'value1', 'key2': 'value2', 'key3': 'value3'}
[ERROR] KeyError: 'resources'
Traceback (most recent call last):
  File "/var/task/lambda_function.py", line 16, in lambda_handler
    volume_arn = event['resources'][0]END RequestId: 3d116529-e903-4b49-9014-c00a5d23a7ca
REPORT RequestId: 3d116529-e903-4b49-9014-c00a5d23a7ca	Duration: 1.55 ms	Billed Duration: 2 ms	Memory Size: 128 MB	Max Memory Used: 60 MB

Request ID
3d116529-e903-4b49-9014-c00a5d23a7ca

Why does it not like resources as a key name?