python - Folium GeoJson自定义颜色图

我正在尝试使用Folium将多部分shapefile显示在 map上。代码如下：

import folium
import gdal
import geopandas as gpd
import branca.colormap as cm

gdf = gpd.read_file("field.shp")

def rank_colormap(gdf):
    if gdf['RANK'] is 1.0:
        return 'red'
    if gdf['RANK'] is 2.0 or 3.0:
        return 'orange'
    if gdf['RANK'] is 4.0:
        return 'gold'
    if gdf['RANK'] is 5.0 or 6.0:
        return 'yellow'
    if gdf['RANK'] is 7.0:
        return 'greenyellow'
    if gdf['RANK'] is 8.0 or 9.0:
        return 'lime'
    elif gdf['RANK'] is 10.0:
        return 'green'

#create map object
m = folium.Map(location=[49.112675, -104.104781], zoom_start=15)
folium.GeoJson(data=gdf, style_function=lambda feature: {
        'fillColor': rank_colormap(gdf),
        'color': 'black',
        'weight': '0.5',
        'fill': True,
        'fill_opacity' : '1'
    }).add_to(m)
tile = folium.TileLayer(
        tiles = 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}',
        attr = 'Esri',
        name = 'Esri Satellite',
        overlay = False,
        control = True
       ).add_to(m)


legendcolormap = cm.LinearColormap(colors=['red', 'orange', 'gold' ,'yellow', 'greenyellow', 'lime', 'green'], vmin=1, vmax=10)
legendcolormap.add_to(m)


#global tooltip
tooltip = 'Click For More Info'

gdf当前看起来像这样，我正在尝试将颜色映射到相应的“ RANK”值：

但是，我的fillcolor调整不正确，仅剩下一种颜色：

如何正确地将色彩图分配给我的叶片图？