Basho\Riak\Node\Config::setPrivateKey PHP Method

    public function setPrivateKey($private_key)
    {
        $this->private_key = $private_key;
    }

 public function withPrivateKey($private_key, $password = '')
 {
     $this->config->setPrivateKey($private_key);
     $this->config->setPrivateKeyPassword($password);
     return $this;
 }