composer package is not installed

[cluster]

I would like to use guzzlehttp with a panel module, but it's not installed ... how can this be solved?

require section of my composer.json module file:

    "require": {
        "blesta/composer-installer": "~1.0",
        "phillipsdata/priority-schedule":"^1.0",
        "guzzlehttp/guzzle": "^7.0"
    }