public function getNewAddressPair($chainIndex = null) {
        $path = $this->getNewDerivation($chainIndex);
        $address = $this->getAddressByPath($path);

        return [$path, $address];
    }
public function getNewAddressPair($chainIndex = null) {
        $path = $this->getNewDerivation($chainIndex);
        $address = $this->getAddressByPath($path);

        return [$path, $address];
    }
public function getNewAddressPair ( $ chainIndex = null ) { $ path = $ this -> getNewDerivation ( $ chainIndex ) ; $ address = $ this -> getAddressByPath ( $ path ) ; return [ $ path , $ address ] ; }
generate a new derived key and return the new path and address for it

@param int|null $chainIndex
@return string[]     [path, address]
generate a new derived key and return the new path and address for it