The snippet below works fine with jsonschema 3.20, but crash with jsonschema 4.0….1:
```python
import pandas as pd
from io import StringIO
df = pd.read_table(StringIO("""
TVCL TVV
0.005298 1.30730
0.006048 1.38692
0.005624 1.53224
0.005771 1.40115
0.005932 1.42119
"""), sep='\s+')
import altair as alt
base = (
alt.Chart(df)
.transform_fold(list(df.columns), as_=['key_x', 'value_x'])
)
```
this is the error:
```
Traceback (most recent call last):
File "<ipython-input-8-50da994c20c5>", line 2, in <module>
alt.Chart(df)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/vegalite/v4/api.py", line 1159, in transform_fold
return self._add_transform(core.FoldTransform(fold=fold, **{"as": as_}))
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/vegalite/v4/schema/core.py", line 18192, in __init__
super(FoldTransform, self).__init__(fold=fold, **kwds)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/vegalite/v4/schema/core.py", line 17975, in __init__
super(Transform, self).__init__(*args, **kwds)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/utils/schemapi.py", line 176, in __init__
self.to_dict(validate=True)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/utils/schemapi.py", line 337, in to_dict
self.validate(result)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/altair/utils/schemapi.py", line 442, in validate
return jsonschema.validate(instance, schema, resolver=resolver)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 965, in validate
error = exceptions.best_match(validator.iter_errors(instance))
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/exceptions.py", line 354, in best_match
best = next(errors, None)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 224, in iter_errors
for error in errors:
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/_validators.py", line 295, in ref
yield from validator.descend(instance, resolved)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 240, in descend
for error in self.evolve(schema=schema).iter_errors(instance):
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 224, in iter_errors
for error in errors:
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/_validators.py", line 329, in properties
yield from validator.descend(
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 240, in descend
for error in self.evolve(schema=schema).iter_errors(instance):
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 224, in iter_errors
for error in errors:
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/_validators.py", line 76, in items
yield from validator.descend(
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 240, in descend
for error in self.evolve(schema=schema).iter_errors(instance):
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 214, in iter_errors
scope = id_of(_schema)
File "/home/devel/pharmpy/.tox/py39/lib/python3.9/site-packages/jsonschema/validators.py", line 90, in _id_of
return schema.get("$id", "")
AttributeError: 'list' object has no attribute 'get'
```