[core] add commanddocs print for UnconstrainedValue

Author: xushengj

src/preppipe/frontend/commanddocs.py

@@ -233,6 +233,8 @@ def get_type_annotation_str_impl(self, a, enumtr_list : list) -> str:
           options.append('"' + '","'.join(enumtr.get_current_candidates()) + '"')
           enumtr_list.append(enumtr)
         return '|'.join(options)
+      if issubclass(a, UnconstrainedValue):
+        return self._tr_any.get()
     raise NotImplementedError(str(a))
 
   def get_default_value_str(self, v) -> str: