I have a GeoDataFrame (let's call it Destinations) that was made from a point shapefile using GeoPandas. For every feature (correct me if the terminology is wrong) in Destinations, I need to find the nearest node on a graph and save that node to another GeoDataFrame (let's call it Destination_nodes, it will be used later for shortest-path analysis). Presumably, this requires creating a new, blank Destination_nodes GeoDataFrame and appending nodes to it as I loop through Destinations. But what is the syntax for creating a new empty GeoDataFrame?