local variable 'tile_ids' referenced before assignment in calling to_flowdataframe(tessellation=tessellation,self_loops=False)

[adhamenaya]

Package version
scikit-mobility: 1.5.3
pandas: 1.3.1
geopandas: 0.10.2
python: 3.8.17

I created a custom tessellation object and I passed it to the to_flowdataframe as follows:
fdf = tdf.to_flowdataframe(tessellation=tessellation,self_loops=False)
This is how I created the tessellation object:

import geopandas as gpd
import h3

# Load a spatial tessellation using H3 hexagons
# Load a spatial tessellation using H3 hexagons
def generate_h3_tessellation(resolution, geo_json_polygon):
    tessellation = []
    tile_ids2 = h3.polyfill(geo_json_polygon, resolution)
    i = 0
    for hex_id in tile_ids2:
        hex_boundary = h3.h3_to_geo_boundary(hex_id, geo_json=True)
        polygon_str = ", ".join([f"{lon} {lat}" for lat, lon in hex_boundary])
        tessellation.append({
            'tile_ID': i,
            'geometry': f'POLYGON (({polygon_str}))'
        })
        i+=1
    return gpd.GeoDataFrame(tessellation, columns=['tile_ID', 'geometry'])


h3_resolution = 7  # Choose a suitable resolution for your analysis

# Define the coordinates for the London bounding box
london_bbox = [
    [-0.510375, 51.286760],  # Bottom-left corner (longitude, latitude)
    [0.334015, 51.691874]    # Top-right corner (longitude, latitude)
]

# Create a Polygon GeoJSON feature for the London bounding box
geo_json_polygon = {
    "type": "Polygon",
    "coordinates": [[
        [london_bbox[0][0], london_bbox[0][1]],
        [london_bbox[0][0], london_bbox[1][1]],
        [london_bbox[1][0], london_bbox[1][1]],
        [london_bbox[1][0], london_bbox[0][1]],
        [london_bbox[0][0], london_bbox[0][1]]
    ]]
}

tessellation = generate_h3_tessellation(h3_resolution, geo_json_polygon)

but I got this error:

---------------------------------------------------------------------------
UnboundLocalError                         Traceback (most recent call last)
Cell In[7], line 1
----> 1 fdf = tdf.to_flowdataframe(tessellation=tessellation,self_loops=False)

File ~/anaconda3/envs/scikit-mobility/lib/python3.8/site-packages/skmob/core/trajectorydataframe.py:244, in TrajDataFrame.to_flowdataframe(self, tessellation, self_loops)
    241 self.sort_values(by=self.__operate_on(), ascending=True, inplace=True)
    243 # Step 2: map the trajectory onto the tessellation
--> 244 flow = self.mapping(tessellation, remove_na=False)
    246 # Step 3: groupby tile_id and sum to obtain the flow
    247 flow.loc[:, constants.DESTINATION] = flow[constants.TILE_ID].shift(-1)

File ~/anaconda3/envs/scikit-mobility/lib/python3.8/site-packages/skmob/core/trajectorydataframe.py:329, in TrajDataFrame.mapping(self, tessellation, remove_na)
    326     tile_ids = utils.nearest(gdf, tessellation, constants.TILE_ID)
    328 new_data = self._constructor(self).__finalize__(self)
--> 329 new_data = new_data.merge(tile_ids, right_index=True, left_index=True)
    331 return new_data

UnboundLocalError: local variable 'tile_ids' referenced before assignment