code: def near(lat, lng, max_dist=None, unit_miles=False):
          
          filters = {
              "$nearSphere": {
                  "$geometry": {
                      "type": "Point",
                      "coordinates": [lng, lat],
                  }
              }
          }
          if max_dist:
              if unit_miles:  # pragma: no cover
                  max_dist = max_dist / 1609.344
              filters["$nearSphere"]["$maxDistance"] = max_dist
          return filters
docs: Find document near a point.
  
          For example:: find all document with in 25 miles radius from 32.0, -73.0.