def __init__(self, slack_token: str, account_id: str, cluster_name: str, signing_key: str, slack_channel: str, is_preview: bool = False):
        """
        Connect to Slack and verify that the Slack token is valid.
        Return True on success, False on failure
        """
        ssl_context = None
        if ADDITIONAL_CERTIFICATE:
            try:
                ssl_context = ssl.create_default_context(cafile=certifi.where())
            except Exception as e:
                logging.exception(f"Failed to use custom certificate. {e}")

        self.slack_client = WebClient(
            token=slack_token,
            ssl=ssl_context,
            timeout=SLACK_REQUEST_TIMEOUT,
            retry_handlers=all_builtin_retry_handlers(),
        )
        self.signing_key = signing_key
        self.account_id = account_id
        self.cluster_name = cluster_name
        self.is_preview = is_preview

        if slack_token not in self.verified_api_tokens:
            try:
                self.slack_client.auth_test()
                self.verified_api_tokens.add(slack_token)
            except SlackApiError as e:
                logging.error(f"Cannot connect to Slack API: {e}")
                raise e

        Connect to Slack and verify that the Slack token is valid.
        Return True on success, False on failure
        
src/robusta/integrations/slack/sender.py