public function toString(): string
    {
        return 'has the key ' . $this->exporter->export($this->key) .
                ' with the value ' . $this->exporter->export($this->value);
    }
public function toString(): string
    {
        return 'has the key ' . $this->exporter->export($this->key) .
                ' with the value ' . $this->exporter->export($this->value);
    }
public function toString ( ) : string { return 'has the key ' . $ this -> exporter -> export ( $ this -> key ) . ' with the value ' . $ this -> exporter -> export ( $ this -> value ) ; }
Returns a string representation of the constraint.

@return string
Returns a string representation of the constraint .