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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def numericalize(self, arr, device=None):
 """Turn a batch of examples that use this field into a Variable. If the field has include_lengths=True, a tensor of lengths will be included in the return value. Arguments: arr (List[List[str]], or tuple of (List[List[str]], List[int])):
 List of tokenized and padded examples, or tuple of List of tokenized and padded examples and List of lengths of each example if self.include_lengths is True. device (str or torch.device):
 A string or instance of `torch.device` specifying which device the Variables are going to be created on. If left as default, the tensors will be created on cpu. Default: None. """

        if self.include_lengths and not isinstance(arr, tuple):
            raise ValueError("Field has include_lengths set to True, but "
                             "input data is not a tuple of "
                             "(data batch, batch lengths).")
        if isinstance(arr, tuple):
            arr, lengths = arr
            lengths = torch.tensor(lengths, dtype=self.dtype, device=device)

        if self.use_vocab:
            if self.sequential:
                arr = [[self.vocab.stoi[x] for x in ex] for ex in arr]
            else:
                arr = [self.vocab.stoi[x] for x in arr]

            if self.postprocessing is not None:
                arr = self.postprocessing(arr, self.vocab)
        else:
            if self.dtype not in self.dtypes:
                raise ValueError(
                    "Specified Field dtype {} can not be used with "
                    "use_vocab=False because we do not know how to numericalize it. "
                    "Please raise an issue at "
                    "https://github.com/pytorch/text/issues".format(self.dtype))
            numericalization_func = self.dtypes[self.dtype]
            # It doesn't make sense to explicitly coerce to a numeric type if
            # the data is sequential, since it's unclear how to coerce padding tokens
            # to a numeric type.
            if not self.sequential:
                arr = [numericalization_func(x) if isinstance(x, six.string_types)
                       else x for x in arr]
            if self.postprocessing is not None:
                arr = self.postprocessing(arr, None)

        var = torch.tensor(arr, dtype=self.dtype, device=device)

        if self.sequential and not self.batch_first:
            var.t_()
        if self.sequential:
            var = var.contiguous()

        if self.include_lengths:
            return var, lengths
        return var