HoughTransform2DCirclesImageFilter cause memory leak in python

My code like this:

```
import itk

image2D = itk.imread('image2D.nii.gz')
hough_filter = itk.HoughTransform2DCirclesImageFilter.New()
hough_filter.SetInput(image2D)
hough_filter.SetNumberOfCircles(1)
hough_filter.SetMinimumRadius(1)
hough_filter.SetMaximumRadius(int(11.4 / 2 / 0.85 + 2))
hough_filter.SetUseImageSpacing(True)

hough_filter.SetSweepAngle(0)
hough_filter.SetSigmaGradient(1)
hough_filter.SetVariance(10)

hough_filter.Update()
circles = hough_filter.GetCircles()
for circle in circles:
print(circle)
```

then I get this:

```
::value_type *' at 0x7fba0c9c8030>
swig/python detected a memory leak of type 'std::list< itkEllipseSpatialObject2_Pointer >::value_type *', no destructor found.
```