def remove_function(self, function_name: str) -> None:
        """
        Remove a function ``function_name`` from the multifunction descriptor.
        """
        if function_name not in self._name_to_source_function:
            raise ValueError(f"function_name {function_name} not found.")
        del self._name_to_source_function[function_name]

        Remove a function ``function_name`` from the multifunction descriptor.
        
coremltools/models/utils.py