'Delete an access key associated with a user.
If the user_name is not specified, it is determined implicitly based
on the AWS Access Key ID used to sign the request.
:type access_key_id: string
:param access_key_id: The ID of the access key to be deleted.
:type user_name: string
:param user_name: The username of the user'

def delete_access_key(self, access_key_id, user_name=None):

    params = {'AccessKeyId': access_key_id}
    if user_name:
        params['UserName'] = user_name
    return self.get_response('DeleteAccessKey', params)
