my_cached_func(2, 21)
```
How to fix an UnhashableTypeError
Streamlit raises this error whenever it encounters a type it doesn't know how to hash. This could be either when hashing the inputs to generate the cache key or when hashing the output to verify whether it changed. To address it, you'll need to help Streamlit understand how to hash that type by using the hash_funcs argument:
python
@st.cache(hash_funcs={FooType: hash_foo_type})
def my_cached_func(a, b):
    ...
Here, FooType is the type Streamlit was unable to hash, and hash_foo_type is a function that can be used to properly hash FooType objects.
For example, if you'd like to make Streamlit ignore a specific type of object when hashing, you can pass a constant function to hash_funcs, like this:
python
@st.cache(hash_funcs={FooType: lambda _: None})
