Add CustomIcon as accepted type of Marker icon

Author: pixelsapphire

folium/map.py

@@ -5,7 +5,7 @@
 
 import warnings
 from collections import OrderedDict
-from typing import List, Optional, Sequence, Union
+from typing import TYPE_CHECKING, List, Optional, Sequence, Union
 
 from branca.element import Element, Figure, Html, MacroElement
 
@@ -21,6 +21,9 @@
     validate_location,
 )
 
+if TYPE_CHECKING:
+    from folium.features import CustomIcon, DivIcon
+
 
 class Evented(MacroElement):
     """The base class for Layer and Map
@@ -373,7 +376,7 @@ def __init__(
         location: Optional[Sequence[float]] = None,
         popup: Union["Popup", str, None] = None,
         tooltip: Union["Tooltip", str, None] = None,
-        icon: Optional[Union[Icon, "DivIcon"]] = None,
+        icon: Optional[Union[Icon, "CustomIcon", "DivIcon"]] = None,
         draggable: bool = False,
         **kwargs: TypeJsonValue,
     ):