Quickbase Pipelines: How to upsert nested JSON array to multi-select text field?

Hello,

I am using  Quickbase Pipelines to pull data from a REST API and save it into a table. I have a "Add a Bulk Upsert Row" step where I am mapping fields from my table to properties of incoming JSON records.

I am facing a challenge around "custom fields" in my JSON records These are fields where instead of simply appearing as "key": "value" pairs in JSON, they appear in a nested array similar to this:

"custom_fields": [
    {
        "key": "street",
        "value": "foo",
    },
    {
        "key": "city",
        "value": "bar",
    },
    {
        "key": "state",
        "value": "baz",
    }
]

I've been able to extract specific values by their key from this structure using this Jinja code block inside my upsert step:

{% for field in d.custom_fields %}
{% if field['key'] == 'street' %}
    {{ field['value'] }}
{% endif %}
{% endfor %}

This works well for Text fields but my first question is - Is this the right way to go about getting in done? Might there be a more succinct way to do this using Jinja?

Unfortunately for me, this technique fails when trying to get a JSON array value into a Multi-Select Text field. 

When I use the a Jinja code block like the one above to parse this bit of JSON:

"custom_fields": [
    {
        "key": "choices",
        "value": [
            "foo,
           "bar",
           "baz"
        ],
    }
]

I get these 3 values in my Multi-Select Text field: [u'foo', u'bar' and u'baz']

It's as if Quickbase / Jinja are parsing the value as a literal string rather than a JSON array.

My second question is therefor - How can I get the above JSON value to be transformed into the correct choices: foo, bar and baz? 

Thanks,
Uri