GraphQL\Error\Error::getPositions PHP Method

    public function getPositions()
    {
        if (null === $this->positions) {
            if (!empty($this->nodes)) {
                $positions = array_map(function ($node) {
                    return isset($node->loc) ? $node->loc->start : null;
                }, $this->nodes);
                $this->positions = array_filter($positions, function ($p) {
                    return $p !== null;
                });
            }
        }
        return $this->positions;
    }

 /**
  * @it converts source and positions to locations
  */
 public function testConvertsSourceAndPositionsToLocations()
 {
     $source = new Source('{
   field
 }');
     $e = new Error('msg', null, $source, [10]);
     $this->assertEquals(null, $e->nodes);
     $this->assertEquals($source, $e->getSource());
     $this->assertEquals([10], $e->getPositions());
     $this->assertEquals([new SourceLocation(2, 9)], $e->getLocations());
 }