[Bug] Predict assert requires LM, make it impossible to derive from BaseLM

[Sciumo]

What happened?

Assertion in Predict makeit impossible to derive from BaseLM, which forces the use of LiteLM no matter what.

assert isinstance(lm, dspy.LM), "No LM is loaded."

dspy/dspy/predict/predict.py

Line 103 in 6307ce4

assert isinstance(lm, dspy.LM), "No LM is loaded."

Steps to reproduce

Create a custom LM drived from BaseLM.

DSPy version

2.6.0

[okhat]

Good point, that's a bug indeed