Update materializecss.py

Author: dwjorgeb

materializecssform/templatetags/materializecss.py

@@ -92,5 +92,5 @@ def is_select(field):
 
 
 @register.filter
-def is_checkbox_select_multiple(field):
-    return isinstance(field.field.widget, forms.CheckboxSelectMultiple)
+def is_select_multiple(field):
+    return isinstance(field.field.widget, forms.SelectMultiple)