Resets the iterator to the beginning of the data.

def reset(self):
        """Resets the iterator to the beginning of the data."""
        if self.shuffle:
            self._shuffle_data()
        # the range below indicate the last batch
        if self.last_batch_handle == 'roll_over' and \
            self.num_data - self.batch_size < self.cursor < self.num_data:
            # (self.cursor - self.num_data) represents the data we have for the last batch
            self.cursor = self.cursor - self.num_data - self.batch_size
        else:
            self.cursor = -self.batch_size