get_field_values has strange behaviour when passing a single field not in a list.

Using a single field for get_field_values results in the following behaviour:


The user should be able to provide a single field, or a list of fields, and receive the expected output. The above example works fine if the single field is put into a list. So that's a possible workaround, but it's inconvenient and unclear for the user.

Locate the get_field_values entry point and reproduce the reported behavior with a single field and with that field wrapped in a list. Compare the outputs and use the list case as the reference; done means both accepted inputs return the expected equivalent result.

Written by the indexing model from the issue text.