fix: prevent shared state between client instances

[calicube]

Summary

The provider_configs field in the Client class was using a mutable default argument (dict = {}). This caused shared state issues where modifying the configuration of one Client instance would inadvertently affect all other instances initialized with the default value.

Changes:

• Changed provider_configs default value from {} to None in Client.__init__.
• Added logic to initialize self.provider_configs as a new dictionary if None is provided.

Root Cause

Default arguments are evaluated only once at function definition time. Using a mutable object like a dictionary as a default argument leads to a persistent object shared across all calls that do not provide an explicit value.

# Problematic behavior in current implementation:
client_a = ai.Client()
client_b = ai.Client()

client_a.configure({"openai": {"api_key": "sk-example"}})

# client_b now unexpectedly contains client_a's config 
# because they both point to the same internal dictionary object.
print(client_b.provider_configs) 
# Output: {'openai': {'api_key': 'sk-example'}}

Solution

def __init__(
    self,
    provider_configs: dict | None = None,
    extra_param_mode: Literal["strict", "warn", "permissive"] = "warn",
):
    self.providers = {}
    # Ensures a fresh dictionary for every instance
    if provider_configs:
        self.provider_configs = provider_configs
    else:
        self.provider_configs = {}
    # ...