fix: raise AttributeError instead of KeyError in __getattr__

[AmSach]

Fixed the bug described in issue #114. Here's what was wrong and how I fixed it:

Problem

DashScopeAPIResponse.getattr raised KeyError when an attribute was missing, but Python's attribute-access protocol requires AttributeError. This broke common Python patterns like getattr(obj, name, default) and hasattr(obj, name) — both rely on AttributeError to trigger the default/fallback path.

Fix

Changed getattr in dashscope/api_entities/dashscope_response.py to catch the KeyError and re-raise it as AttributeError:

def __getattr__(self, attr):
    try:
        return self[attr]
    except KeyError:
        raise AttributeError(attr) from None

Tested by

All 4 test cases pass:

• getattr(response, 'missing', 'default') → returns 'default' ✓
• hasattr(response, 'missing') → returns False ✓
• response.existing_attr → still works correctly ✓
• response.missing_attr → raises AttributeError (correct) ✓

Fixes: #114

[gemini-code-assist]

Code Review

This pull request updates the getattr method in dashscope/api_entities/dashscope_response.py to handle missing keys by raising an AttributeError instead of a KeyError. The reviewer suggests enhancing the error message to include the class name, which would improve debugging clarity and align with standard Python error reporting.

[gemini-code-assist]

While raising AttributeError correctly fixes the reported issue, the error message could be improved to follow standard Python conventions. Currently, it only provides the attribute name, which results in a terse error like AttributeError: missing_attr. A more descriptive message including the class name (e.g., AttributeError: 'DashScopeAPIResponse' object has no attribute 'missing_attr') would be more helpful for debugging and consistent with built-in Python behavior.

Suggested change

	raise AttributeError(attr) from None
	raise AttributeError(f"'{type(self).__name__}' object has no attribute '{attr}'") from None