code: def _coord2int(lng, lat, dim):
      
      assert dim >= 1
  
      lat_y = (lat + _LAT_INTERVAL[1]) / 180.0 * dim   # [0 ... dim)
      lng_x = (lng + _LNG_INTERVAL[1]) / 360.0 * dim  # [0 ... dim)
  
      return min(dim - 1, int(floor(lng_x))), min(dim - 1, int(floor(lat_y)))
docs: Convert lon, lat values into a dim x dim-grid coordinate system.
  
      Parameters:
          lng: float    Longitude value of coordinate (-180.0, 180.0); corresponds to X axis
          lat: float    Latitude value of coordinate (-90.0, 90.0); corresponds to Y axis
          dim: int      Number of coding points each x, y value can take.
                        Corresponds to 2^level of the hilbert curve.
  
      Returns:
          Tuple[int, int]:
              Lower left corner of corresponding dim x dim-grid box
                x      x value of point [0, dim); corresponds to longitude
                y      y value of point [0, dim); corresponds to latitude