MLflow seems to have a length limit of 5000 when setting tags (see below).

[...]
  File "/home/smay/miniconda3/envs/py38/lib/python3.8/site-packages/mlflow/utils/validation.py", line 136, in _validate_length_limit
    raise MlflowException(
mlflow.exceptions.MlflowException: Tag value '[0.8562690322984875, 0.8544098885636596, 0.8544098885636596, 0.8544098885636596, 0.85440988856365

This is more a question than a feature request.

When parsing JSON files, I need to sanitize the field names so field with spaces becomes field_with_spaces.
I want to preserve the original name as well, metadata about the column if you like :)

There is a metadata field on StructField, but it is internal.
Why is this internal, is it possible or desirable to expose it?