Error when calculating glue score
The glue metric for cola is a metric for classification. It expects label ids as integers as inputs.
I was trying glue score along with other metrics here. But glue gives me this error;

```
import nlp
glue_metric = nlp.load_metric('glue',name="cola")

glue_score = glue_metric.compute(predictions, references)
```

```
---------------------------------------------------------------------------
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-b9210a524504> in <module>()
----> 1 glue_score = glue_metric.compute(predictions, references)

6 frames
/usr/local/lib/python3.6/dist-packages/nlp/metric.py in compute(self, predictions, references, timeout, **metrics_kwargs)
    191         """
    192         if predictions is not None:
--> 193             self.add_batch(predictions=predictions, references=references)
    194         self.finalize(timeout=timeout)
    195 

/usr/local/lib/python3.6/dist-packages/nlp/metric.py in add_batch(self, predictions, references, **kwargs)
    207         if self.writer is None:
    208             self._init_writer()
--> 209         self.writer.write_batch(batch)
    210 
    211     def add(self, prediction=None, reference=None, **kwargs):

/usr/local/lib/python3.6/dist-packages/nlp/arrow_writer.py in write_batch(self, batch_examples, writer_batch_size)
    155         if self.pa_writer is None:
    156             self._build_writer(pa_table=pa.Table.from_pydict(batch_examples))
--> 157         pa_table: pa.Table = pa.Table.from_pydict(batch_examples, schema=self._schema)
    158         if writer_batch_size is None:
    159             writer_batch_size = self.writer_batch_size

/usr/local/lib/python3.6/dist-packages/pyarrow/types.pxi in __iter__()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib.asarray()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib.array()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib._sequence_to_array()

TypeError: an integer is required (got type str)
```
I'm not sure whether I'm doing this wrong or whether it's an issue. I would like to know a workaround. Thank you.
Error when calculating glue score 
 I was trying glue score along with other metrics here. But glue gives me this error;

```
import nlp
glue_metric = nlp.load_metric('glue',name="cola")

glue_score = glue_metric.compute(predictions, references)
```

```
---------------------------------------------------------------------------
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-8-b9210a524504> in <module>()
----> 1 glue_score = glue_metric.compute(predictions, references)

6 frames
/usr/local/lib/python3.6/dist-packages/nlp/metric.py in compute(self, predictions, references, timeout, **metrics_kwargs)
    191         """
    192         if predictions is not None:
--> 193             self.add_batch(predictions=predictions, references=references)
    194         self.finalize(timeout=timeout)
    195 

/usr/local/lib/python3.6/dist-packages/nlp/metric.py in add_batch(self, predictions, references, **kwargs)
    207         if self.writer is None:
    208             self._init_writer()
--> 209         self.writer.write_batch(batch)
    210 
    211     def add(self, prediction=None, reference=None, **kwargs):

/usr/local/lib/python3.6/dist-packages/nlp/arrow_writer.py in write_batch(self, batch_examples, writer_batch_size)
    155         if self.pa_writer is None:
    156             self._build_writer(pa_table=pa.Table.from_pydict(batch_examples))
--> 157         pa_table: pa.Table = pa.Table.from_pydict(batch_examples, schema=self._schema)
    158         if writer_batch_size is None:
    159             writer_batch_size = self.writer_batch_size

/usr/local/lib/python3.6/dist-packages/pyarrow/types.pxi in __iter__()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib.asarray()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib.array()

/usr/local/lib/python3.6/dist-packages/pyarrow/array.pxi in pyarrow.lib._sequence_to_array()

TypeError: an integer is required (got type str)
```
I'm not sure whether I'm doing this wrong or whether it's an issue. I would like to know a workaround. Thank you. 
 The glue metric for cola is a metric for classification. It expects label ids as integers as inputs.