Fix ClaudeModel support.

src/lm.py

@@ -12,6 +12,11 @@
 from dsp.modules.hf_client import send_hfvllm_request_v00, send_hftgi_request_v01_wrapped
 from transformers import AutoTokenizer
 
+try:
+ import anthropic
+except ImportError:
+ pass
+
 
 class OpenAIModel(dspy.OpenAI):
  """A wrapper class for dspy.OpenAI."""
@@ -115,7 +120,7 @@ def __init__(
  ):
  super().__init__(model)
  try:
- from anthropic import Anthropic, RateLimitError
+ from anthropic import Anthropic
  except ImportError as err:
  raise ImportError("Claude requires `pip install anthropic`.") from err
 
@@ -188,7 +193,7 @@ def basic_request(self, prompt: str, **kwargs):
 
  @backoff.on_exception(
  backoff.expo,
- (RateLimitError,),
+ (anthropic.RateLimitError,),
  max_time=1000,
  max_tries=8,
  on_backoff=backoff_hdlr,
@@ -219,8 +224,11 @@ def __call__(self, prompt, only_completed=True, return_sorted=False, **kwargs):
  for _ in range(n):
  response = self.request(prompt, **kwargs)
  self.log_usage(response)
- if only_completed and response.stop_reason == "max_tokens":
- continue
+ # This is the original behavior in dspy/dsp/modules/anthropic.py.
+ # Comment it out because it can cause "IndexError: list index out of range" silently
+ # which is not transparent to developers.
+ # if only_completed and response.stop_reason == "max_tokens":
+ # continue
  completions = [c.text for c in response.content]
  return completions