Fix type annotation for xml_to_string

lib/galaxy/tool_util/data/__init__.py

@@ -880,13 +880,11 @@ def to_dict(self, view: str = "collection", value_mapper: Optional[Dict[str, Cal
 
 
 @overload
-def _expand_here_template(content: str, here: Optional[str]) -> str:
-    ...
+def _expand_here_template(content: str, here: Optional[str]) -> str: ...
 
 
 @overload
-def _expand_here_template(content: None, here: Optional[str]) -> None:
-    ...
+def _expand_here_template(content: None, here: Optional[str]) -> None: ...
 
 
 def _expand_here_template(content: Optional[str], here: Optional[str]) -> Optional[str]:

lib/galaxy/util/__init__.py

@@ -391,15 +391,14 @@ def parse_xml_string_to_etree(xml_string: str, strip_whitespace: bool = True) ->
     return ElementTree(parse_xml_string(xml_string=xml_string, strip_whitespace=strip_whitespace))
 
 
-def xml_to_string(elem: Element, pretty: bool = False) -> str:
+def xml_to_string(elem: Optional[Element], pretty: bool = False) -> str:
     """
     Returns a string from an xml tree.
     """
+    if elem is None:
+        return ""
     try:
-        if elem is not None:
-            xml_str = etree.tostring(elem, encoding="unicode")
-        else:
-            xml_str = ""
+        xml_str = etree.tostring(elem, encoding="unicode")
     except TypeError as e:
         # we assume this is a comment
         if hasattr(elem, "text"):