    def __init__(self, username, token, icon_url):
        # type: (str, str, str) -> None
        '''
        Constructs the Slack API object using the bot's username, a Slack
        token, and a URL to what the bot's profile pic should be.
        '''
        self._username = username
        self._icon_url = icon_url

        self._slack = SlackClient(token)
        self._validate()
Constructs the Slack API object using the bot's username, a Slack
token, and a URL to what the bot's profile pic should be.
securitybot/chat/slack.py