"column" property not allowed when trying to create facet chart with arc in Vega-lite (Deneb)

Question

I am trying to create a faceted donut chart in PowerBI using Deneb, and Vega-lite. However, when I try to add faceting to my existing chart, I get an error saying that "facet" or "column" are not allowed in the "encoding" section.

I tried using the code shown on the Vega-lite github pie and donut charts example page here to create multiples of the donut chart using "column". I also tried using "facet". However, both resulted in an error that reads "Property column [facet] is not allowed."

This is under the Spec section of Deneb. My code:

{
  "data": {
    "name": "dataset"
  },
  "layer": [
    {
      "description": "Outer donut for showing the KPI % measure",
      "mark": {
        "type": "arc",
        "radius": 98,
        "radius2": 70
      },
      "encoding": {
        "column": {
          "field": "Location_ID"
        },
        "theta": {
          "field": "Result_umol-L",
          "type": "quantitative",
          "aggregate": "sum"
        },
        "color": {
          "field": "Data Color Fixed",
          "type": "nominal",
          "scale": null
        }
      }
    }
    {
      "description": "KPI text inside the donut",
      "mark": {
        "type": "text",
        "yOffset": 7,
        "baseline": "bottom",
        "font": "DIN",
        "fontSize": 20,
        "fontWeight": "bold",
        "color": "#000000"
      },
      "encoding": {
        "text": {
          "aggregate": "sum",
          "field": "Result",
          "type": "quantitative",
          "format": "0.0 ug/L",
          "formatType": "pbiFormat"
        }
      }
    },
    {
      "description": "Location text inside donut",
      "mark": {
        "type": "text",
        "yOffset": 7,
        "baseline": "top",
        "font": "DIN",
        "fontSize": 20,
        "fontWeight": "bold",
        "color": "#000000"
      },
      "encoding": {
        "text": {
          "aggregate": "min",
          "field": "Location_ID",
          "type": "nominal",
          "formatType": "pbiFormat"
        }
      }
    }
  ]
}