title: Using rgee and fastDistanceTransform with a featureCollection
body: <p>I have successfully extracted distance to nearest human settlement with rgee function fastDistanceTransform, where the original layer is a single image (DLR/WSF/WSF2015/v1). I want to repeat this with distance to nearest road, but the road dataset is a featureCollection and not an image.</p>
  <p>I have successfully converted to image in the gee code editor with:</p>
  <pre><code>var dataset = ee.FeatureCollection('TIGER/2016/Roads')
  .map(function(feature){
      var num = ee.Number.parse(feature.get('linearid'));
      return feature.set('linearid', num);
  });
  
    var roads = dataset
    .reduceToImage({
      properties: ['linearid'],
      reducer: ee.Reducer.first()
  });
  
  Map.setCenter(-99.976, 40.38, 5);
  Map.addLayer(roads, {
  });
  </code></pre>
  <p>But I cannot get it to repeat the same in the R package rgee. I am using code:</p>
  <pre><code>road = ee$FeatureCollection(&quot;TIGER/2016/Roads&quot;)$
    map(function(feature) { num = ee$Number$parse(feature$get('linearid'))
    return(feature$set('linearid', num)) })
  road2 = road$reduceToImage(properties=road$select('linearid'), reducer=ee$Reducer$first())
  Map$addLayer(road2, {}, &quot;road2&quot;)
  </code></pre>
  <p>But I get the error:</p>
  <pre><code>Error in py_call_impl(callable, dots$args, dots$keywords) : 
  ee.ee_exception.EEException: Collection.reduceToImage, argument 'properties': Invalid type.
  Expected type: List&lt;String&gt;.
  Actual type: FeatureCollection.
  </code></pre>
  <p>Can anyone help me fix this error so I can continue using 'road2' as an image? I think it has something to do with this (<a href="https://github.com/r-spatial/rgee/issues/232" rel="nofollow noreferrer">https://github.com/r-spatial/rgee/issues/232</a>) &quot;It seems that passing an ee.Image object in Javascript immediately changes it to a List&quot;</p>