docs: def export_probability(outputname, **kwargs):
      """
          Calculate probability and export to gis raster/grid
          format. 
          
          export_probability(prob_out,
                             trajectory_files = [myfiles1.nc, myfiles2.nc],
                             bbox = [-75, 23, -60, 45],
                             nx = 1000, ny = 1000,
                             method = 'overall')  
      """
      bbox = kwargs.get('bbox', None)
      nx, ny = kwargs.get('nx', None), kwargs.get('ny', None)
      if bbox == None:
          raise ValueError('Must supply bbox keyword argument.')
      if nx == None or ny == None:
          raise ValueError('Must supply nx and ny keyword arguments.')
      prob = compute_probability(**kwargs)
      export_grid(outputname, prob, bbox, nx, ny)