def get_function_type(self):
        """Return unique function type of dispatcher when possible, otherwise
        return None.

        A Dispatcher instance has unique function type when it
        contains exactly one compilation result and its compilation
        has been disabled (via its disable_compile method).
        """
        if not self._can_compile and len(self.overloads) == 1:
            cres = tuple(self.overloads.values())[0]
            return types.FunctionType(cres.signature)
Return unique function type of dispatcher when possible, otherwise
        return None.

        A Dispatcher instance has unique function type when it
        contains exactly one compilation result and its compilation
        has been disabled (via its disable_compile method).
        
numba/core/dispatcher.py