[🐛 Bug Report]: Visualization draw_model function crashes on None/Null

Describe the bug

From the This example notebook Visualization.ipynb: Call to neuralogic.utils.visualize.draw_model function, draw_model(model), results in the following error:

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-7-59797e1249fd> in <module>
      7 model = template.build(Backend.JAVA, Settings())
      8 
----> 9 draw_model(model)

...\lib\site-packages\neuralogic\utils\visualize\__init__.py in draw_model(model, filename, draw_ipython, img_type, value_detail, *args, **kwargs)
     93     template_drawer = get_template_drawer(get_drawing_settings(img_type=img_type, value_detail=value_detail))
     94 
---> 95     return draw(template_drawer, template, filename, draw_ipython, img_type, *args, **kwargs)
     96 
     97 

...\lib\site-packages\neuralogic\utils\visualize\__init__.py in draw(drawer, obj, filename, draw_ipython, img_type, *args, **kwargs)
     55         return
     56 
---> 57     data = bytes(drawer.drawIntoBytes(obj))
     58 
     59     if draw_ipython:

TypeError: cannot convert 'NoneType' object to bytes

---

Similarly, adding a filename to the call (draw_model(model, 'img.png'), see code snippets below) results in a NullPointerException:

---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
...\lib\site-packages\_jpype.cp38-win_amd64.pyd in cz.cvut.fel.ida.drawing.Drawer.drawIntoFile()

...\lib\site-packages\_jpype.cp38-win_amd64.pyd in cz.cvut.fel.ida.drawing.GraphViz.writeImageToFile()

~\Anaconda3\envs\bakalarka\lib\site-packages\_jpype.cp38-win_amd64.pyd in java.io.FileOutputStream.write()

Exception: Java Exception

The above exception was the direct cause of the following exception:

java.lang.NullPointerException            Traceback (most recent call last)
<ipython-input-8-91eec29cdcf5> in <module>
      7 model = template.build(Backend.JAVA, Settings())
      8 
----> 9 draw_model(model, 'img.png')

...\lib\site-packages\neuralogic\utils\visualize\__init__.py in draw_model(model, filename, draw_ipython, img_type, value_detail, *args, **kwargs)
     93     template_drawer = get_template_drawer(get_drawing_settings(img_type=img_type, value_detail=value_detail))
     94 
---> 95     return draw(template_drawer, template, filename, draw_ipython, img_type, *args, **kwargs)
     96 
     97 

...\lib\site-packages\neuralogic\utils\visualize\__init__.py in draw(drawer, obj, filename, draw_ipython, img_type, *args, **kwargs)
     51 def draw(drawer, obj, filename: Optional[str] = None, draw_ipython=True, img_type="png", *args, **kwargs):
     52     if filename is not None:
---> 53         drawer.drawIntoFile(obj, os.path.abspath(filename))
     54 
     55         return

java.lang.NullPointerException: java.lang.NullPointerException

Steps to reproduce the behavior

I have come across this error in my own example codes, but it is enough to run the Visualization.ipynb notebook, concretely:

from neuralogic.utils.visualize import draw_model
from neuralogic.utils.data import XOR_Vectorized
from neuralogic.core import Settings, Backend


template, dataset = XOR_Vectorized()
model = template.build(Backend.JAVA, Settings())

draw_model(model)

---

For the NullPointerException, I used:

from neuralogic.utils.visualize import draw_model
from neuralogic.utils.data import XOR_Vectorized
from neuralogic.core import Settings, Backend


template, dataset = XOR_Vectorized()
model = template.build(Backend.JAVA, Settings())

draw_model(model, 'img.png')

Expected behavior

I should be able to visualize the model.

Environment

No response

Additional context

No response

[borisrakovan]

I bumped the version to 0.1.5 and the drawing works fine on macOS. Thanks. Unfortunately I don’t have rights to close the issue.

[martin-krutsky]

I can confirm it works for me on Windows, both in the visualization notebook and in my own experiment. Thanks! @borisrakovan, feel free to close this issue, if you can confirm the issue is solved on macOS, as well.