[WIP] Fix bug in segment chemical structures from file method

[Copilot]

• Analyze the issue with model download from Zenodo
• Add better error handling for network failures in load_model()
• Add informative error messages with instructions for manual download
• Add timeout parameter to requests.get() to prevent indefinite hanging
• Test the changes with simulated network failure scenarios

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Bugs for using the method 'segment_chemical_structures_from_file'</issue_title>
<issue_description>When I use the method 'segment_chemical_structures_from_file', it goes error like:

HTTPSConnectionPool(host='zenodo.org', port=443): Max retries exceeded with url: /record/10663579/files/mask_rcnn_molecule.h5?download=1 (Caused by NewConnectionError('<urllib3.connection.HTTPSConnection object at 0x7e7581a0f520>: Failed to establish a new connection: [Errno 111] Connection refused')

What's wrong of that? It occurs to the phase of model downloading...

Hopefully you can help me!</issue_description>

<agent_instructions>If the author does not reply within 2 weeks of time close it</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@Kohulan Hi @HenryStephen ,

Could you check whether your environment has a stable internet connection? On the first run, the package tries to automatically download the model (mask_rcnn_molecule.h5) from Zenodo. The error message suggests the connection to zenodo.org was refused, which usually points to a network issue (firewall, VPN, or temporary outage).

If you’re behind a firewall or proxy, you may need to adjust your settings

Fixes #127

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.