Python: unhashable type exception for custom return type in kernel function

Describe the bug

TypeError: unhashable type: 'AccountBalance'

I am using a kernel function that returns a custom type:

    @kernel_function(description="Get user account balance")
    async def get_user_account_balance(self, account_id: str) -> "AccountBalance":
        //....
        return AccountBalance(account_balance=account_balance)

    class AccountBalance(BaseModel):
          balance: int = Field(..., alias="account_balance")

To Reproduce
Steps to reproduce the behavior:

Create an agent group chat
Add an agent to the group chat with a kernel function that returns a custom type such as AccountBalance
Invoke the agent through the group chat and let the agent invoke the kernel function that returns a list
See error

Expected behavior
Custom types in kernel function should work

Screenshots
If applicable, add screenshots to help explain your problem.

Platform

Language: Python
Source: 1.19.0
IDE: VS Code]
OS: Mac

Additional context

  File "/demo/.venv/lib/python3.12/site-packages/semantic_kernel/agents/group_chat/agent_group_chat.py", line 144, in invoke
    async for message in super().invoke_agent(selected_agent):
  File "/demo/.venv/lib/python3.12/site-packages/semantic_kernel/agents/group_chat/agent_chat.py", line 144, in invoke_agent
    async for is_visible, message in channel.invoke(agent):
  File "/demo/.venv/lib/python3.12/site-packages/semantic_kernel/agents/channels/chat_history_channel.py", line 75, in invoke
    mutated_history.add(mutated_message)
  File "/demo/.venv/lib/python3.12/site-packages/semantic_kernel/contents/chat_message_content.py", line 318, in __hash__
    return hash((self.tag, self.role, self.content, self.encoding, self.finish_reason, *self.items))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/demo/.venv/lib/python3.12/site-packages/semantic_kernel/contents/function_result_content.py", line 197, in __hash__
    return hash((
           ^^^^^^
TypeError: unhashable type: 'AccountBalance'

Abhishek Gupta (@abhirockzz)

Hi Abhishek Gupta (@abhirockzz), we'll improve the handling for types so the hash doesn't error. To unblock you right now, I'd advise that you make you freeze your BaseModel like:

class AccountBalance(BaseModel):
    # Make the model frozen so it's hashable
    balance: int = Field(..., alias="account_balance")
    model_config = ConfigDict(frozen=True)

I tested this with:

def test_hash_with_frozen_account_balance():
    balance = AccountBalance(account_balance=100)
    content = FunctionResultContent(
        id="test_id",
        result=balance,
        function_name="TestFunction",
    )
    # Verify we can call hash without error
    _ = hash(content)
    assert True, "Hashing FunctionResultContent with frozen model should not raise errors."

and this passes. That would be the quickest way to handle it now while we make some improvements. Thanks for filing the issue.

Python: Allow enums to be passed in to on_function_result. Improve ha…

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Python: unhashable type exception for custom return type in kernel function #10299

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Python: unhashable type exception for custom return type in kernel function #10299

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moonbox3 commented on Jan 28, 2025

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