code: def getUnionLocations(encoder, x, y, r, step=1):
    
    output = np.zeros(encoder.getWidth(), dtype=defaultDtype)
    locations = set()
    for dx in range(-r, r+1, step):
      for dy in range(-r, r+1, step):
        if dx*dx + dy*dy <= r*r:
          e = encodeLocation(encoder, x+dx, y+dy, output)
          locations = locations.union(set(e))
  
    return locations
docs: Return a union of location encodings that correspond to the union of all locations
    within the specified circle.