VegaLite.jl: How to pass in a DataFrame and apply data parameters

When I pipe a DataFrame into @vlplot I’m not able to call the additional configuration parameters as the data isn’t inline. Below is what I want to achieve, but using an external DataFrame as the values:

    data = {
    values = [{foo="Jan",bar=1.7},{foo="Feb",bar=1.5},{foo="Mar",bar=0.8}],
    format = {parse ={"foo"= "utc:'%b'"}}

I see the shorthand way to specify a DataFrame as inline in the VegaLite.jl documentation as below, but if I set values equal to the DataFrame in the verbose data format (above), it doesn’t import into the spec in a useable way.

@vlplot(:point, data=df, x=:a, y=:b)

Can anyone tell me how to go about this?