Sets the current read pointer position.

        This function is internally called by `read_idx(idx)` to find the current
        reader pointer position. It doesn't return anything.

def seek(self, idx):
        """Sets the current read pointer position.

        This function is internally called by `read_idx(idx)` to find the current
        reader pointer position. It doesn't return anything."""
        assert not self.writable
        self._check_pid(allow_reset=True)
        pos = ctypes.c_size_t(self.idx[idx])
        check_call(_LIB.MXRecordIOReaderSeek(self.handle, pos))