Python Bokeh:中的fill_color问题。除零值外，Choropleth填充为灰色。可能是范围问题？

from bokeh.io import output_file, show
from bokeh.models import ColorBar, LogColorMapper
from bokeh.palettes import Viridis256
from bokeh.plotting import figure
from bokeh.sampledata.us_counties import data as counties

# 准备数据
county_xs = [county["lons"] for county in counties.values()]
county_ys = [county["lats"] for county in counties.values()]
county_names = [county['name'] for county in counties.values()]
county_rates = [county['rate'] for county in counties.values()]

# 创建Choropleth图表
p = figure(title="Choropleth Map", toolbar_location="left",
           plot_width=800, plot_height=500)
p.patches(county_xs, county_ys, fill_color=LogColorMapper(palette=Viridis256,
              low=min(county_rates), high=max(county_rates)),
          line_color="gray", line_width=0.5)

# 添加颜色条
color_bar = ColorBar(color_mapper=LogColorMapper(palette=Viridis256,
                     low=min(county_rates), high=max(county_rates)),
                     label_standoff=12)
p.add_layout(color_bar, 'right')

# 显示图表
show(p)