add fpdb for multiprocess debugging using pdb

[aniketmaurya]

What does this PR do?

Users will be able to set_trace for debugging.

Example

import litserve as ls

class SimpleLitAPI(ls.LitAPI):
    def setup(self, device):
        self.model1 = lambda x: x**2
        self.model2 = lambda x: x**3

    def decode_request(self, request):
        # get inputs to /predict
        return request["input"]

    def predict(self, x):
        # perform calculations using both models
        a = self.model1(x)
        ls.set_trace()
        b = self.model2(x)
        c = a + b
        return {"output": c}

    def encode_response(self, output):
        # package outputs from /predict
        return {"output": output}

if __name__ == "__main__":
    server = ls.LitServer(SimpleLitAPI(max_batch_size=1), accelerator="auto")
    server.run(port=8000)

• Added set_trace and set_trace_if_debug functions to litserve/utils.py for debugging support.
• Updated litserve/__init__.py to import new debugging utilities.
• Added unit tests for set_trace_if_debug to ensure correct behavior based on the LITSERVE_DEBUG environment variable.

Before submitting

• Was this discussed/agreed via a Github issue? (no need for typos and docs improvements)
• Did you read the contributor guideline, Pull Request section?
• Did you make sure to update the docs?
• Did you write any new necessary tests?

PR review

Anyone in the community is free to review the PR once the tests have passed.
If we didn't discuss your PR in GitHub issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 86%. Comparing base (7fcbdfb) to head (a192436).
Report is 2 commits behind head on main.

Additional details and impacted files

@@         Coverage Diff         @@
##           main   #508   +/-   ##
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- Coverage    86%    86%   -0%     
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  Files        37     37           
  Lines      2373   2386   +13     
===================================
+ Hits       2046   2054    +8     
- Misses      327    332    +5     

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[lianakoleva]

looks great! will be useful, just one small ask