Pickle alternatives

Pickle is not safe. An alternative implementation may use [PyArrow](https://arrow.apache.org/docs/python/ipc.html#arbitrary-object-serialization) instead:

```python
import pyarrow as pa
import pandas as pd

pa.serialize_to(dict_of_data, r'/path/to/file.a')
data = pa.deserialize_from(r'/path/to/file.a', pd.DataFrame)
type(data)  # dict
```

