How should i run this file in gitlab.ci.yml script to clean?

So This is the Python file i have with me

clean_old_lambda_versions.py

from __future__ import absolute_import, print_function, unicode_literals
import boto3

# This script removes all versions except $LATEST and the newest version
# If this script tries to delete a version any alias is using,
# boto3 will throw an exception and the script will exit

def clean_old_lambda_versions():
    client = boto3.client('lambda')
    functions = client.list_functions()['Functions']
    for function in functions:
        while True:
          versions = client.list_versions_by_function(FunctionName=function['FunctionArn'])['Versions']
          numVersions = len(versions)
          if numVersions <= 2:
              print('{}: done'.format(function['FunctionName']))
              break
          for version in versions:
              if version['Version'] != function['Version'] and numVersions > 2: # $LATEST
                  arn = version['FunctionArn']
                  print('delete_function(FunctionName={})'.format(arn))
                  # client.delete_function(FunctionName=arn)  # uncomment me once you've checked
                  numVersions -= 1


if __name__ == '__main__':
    clean_old_lambda_versions()

And this is my gitlab.ci.yml file to execute this file

delete-lambda-versions-nonprod:
  stage: import
  image: "someimage/confidential"
  <<: *nonprod
  variables:
    ENV_TAG: "alpha1"
  script:
     - . ./clean_old_lambda_versions.py
  when: manual

This is the error i am getting when running this pipeline in my gitlab

$ . ./clean_old_lambda_versions.py /bin/sh: ./clean_old_lambda_versions.py: line 1: import: not found

Can someone help me with this. How can i execute this script and clean all my older versions in aws lambda ? or is there any other work around to clean the older version using jobs in gitlab ? Thanks in advance