Explicitly drop this pointer.  The memory will be deallocated via
        the drop_ffi_call_fn passed to the constructor.

def drop(self):
        """Explicitly drop this pointer.  The memory will be deallocated via
        the drop_ffi_call_fn passed to the constructor.
        """
        if self._ptr:
            LIBRARY.call(self._drop_ffi_fn, self._ptr)
            self._ptr = None