Extend ``as_data_frame()`` method for more than one field

[GuillemBarroso]

Description of the feature

The DataObject method as_data_frame() is currently only implemented for FieldsContainers with only one Field.

This should be extended to any number of fields.

Steps for implementing the feature

Modify the as_data_frame() method to be able to accept FieldsContainers with more than one Field.

Useful links and references

N/A

[PProfizi]

Closing as stale