How to use the padding.pad_dataset function in Padding

def _pad(self, side, length):
        """
        Pad sequences to given length in the left or right side.
        """
        if self._train_set:
            self._train_set = pad_dataset(self._train_set, side, length)
        if self._valid_set:
            self._valid_set = pad_dataset(self._valid_set, side, length)
        if self._test_set:
            self._test_set = pad_dataset(self._test_set, side, length)

def _pad(self, side, length):
        """
        Pad sequences to given length in the left or right side.
        """
        if self._train_set:
            self._train_set = pad_dataset(self._train_set, side, length)
        if self._valid_set:
            self._valid_set = pad_dataset(self._valid_set, side, length)
        if self._test_set:
            self._test_set = pad_dataset(self._test_set, side, length)

def _pad(self, side, length):
        """
        Pad sequences to given length in the left or right side.
        """
        if self._train_set:
            self._train_set = pad_dataset(self._train_set, side, length)
        if self._valid_set:
            self._valid_set = pad_dataset(self._valid_set, side, length)
        if self._test_set:
            self._test_set = pad_dataset(self._test_set, side, length)

def _yield_data(self, subset):
        for i in xrange(0, len(subset), self.size):
            x_set, y_set = [], []
            batch = pad_dataset(subset[i:i + self.size], PADDING_SIDE, self.padding_length)
            for x, y in batch:
                x_set.append(x)
                y_set.append(y)
            x_set = np.array(x_set)
            y_set = np.array(y_set)
            if self._fix_batch_size and x_set.shape[0] != self.size:
                continue
            yield x_set, y_set