Function FLMutableDict_GetMutableDict 

pub unsafe extern "C" fn FLMutableDict_GetMutableDict(
    arg1: FLMutableDict,
    key: FLString,
) -> FLMutableDict

Convenience function for getting a dict-valued property in mutable form.

• If the value for the key is not a dict, returns NULL.
• If the value is a mutable dict, returns it.
• If the value is an immutable dict, this function makes a mutable copy, assigns the copy as the property value, and returns the copy.