How to fix ValueError: not enough values to unpack (expected 2, got 0) in bb

[douding-lhy]

This is my code and I want to visualize the gpx data for testing.

`from leuvenmapmatching.util.gpx import gpx_to_path
from leuvenmapmatching.matcher.distance import DistanceMatcher
from leuvenmapmatching.map.inmem import InMemMap
from leuvenmapmatching import visualization as mmviz

map_con = InMemMap("mymap", use_latlon=False)

track = gpx_to_path("route.gpx")
matcher = DistanceMatcher(map_con,
max_dist=100, max_dist_init=25, # meter
min_prob_norm=0.001,
non_emitting_length_factor=0.75,
obs_noise=50, obs_noise_ne=75, # meter
dist_noise=50, # meter
non_emitting_states=True,
max_lattice_width=5)
states, lastidx = matcher.match(track)

mmviz.plot_map(map_con, matcher=matcher,
use_osm=True, zoom_path=True,
show_labels=False, show_matching=True, show_graph=False,
filename="my_osm_plot.png")`

However, the following error appear.

Traceback (most recent call last):
File "C:\Users\Jason...\Data_prep\MapMatching.py", line 20, in
mmviz.plot_map(map_con, matcher=matcher,
File "C:\Users\Jason...\Data_prep\venv\Lib\site-packages\leuvenmapmatching\visualization.py", line 62, in plot_map
bb = map_con.bb()
^^^^^^^^^^^^
File "C:\Users\Jason...\Data_prep\venv\Lib\site-packages\leuvenmapmatching\map\inmem.py", line 187, in bb
glat, glon = zip(*[t[0] for t in self.graph.values()])
^^^^^^^^^^
ValueError: not enough values to unpack (expected 2, got 0)

Please, I wanna know how to fix it.