constructor(endpoint, stream_type, config={}) {
        this.stream_type = stream_type;
        this.endpoint = endpoint;
        this.eventSource = new EventEmitter();
        this.dataQueue = [];
    }
Returns the pem encoded representation of the public key
If the key doesn't exists a new key will be created
@returns {string} pem encoded representation of the public key WITHOUT header and footer
@public