Add function to ensure a non-empty string.

src/jcloud_docsgen/utils.py

@@ -127,4 +127,28 @@ def assert_that_is_instance(obj: object, class_or_tuple: Union[type, types.Union
             exception_message_expected += human_readable_list(_list_type_names(class_or_tuple), 'or', '\'')
         else:
             exception_message_expected = '\'' + class_or_tuple.__name__ + '\''
-        raise TypeError(f'expected {exception_message_expected}, got \'{type(obj).__name__}\'')
+        raise TypeError(f'expected {exception_message_expected}, got \'{type(obj).__name__}\'')
+    
+def non_empty_str(value: Union[str, None]) -> Union[str, None]:
+    '''
+    Returns the value or ``None``.
+
+    Returns the value if it is not empty and not `Ǹone``; otherwise,
+    returns ``None``.
+    Please note: values are stripped, i. e. if the value consists only
+                 of spaces, it is also considered empty.
+
+    :param value: The value.
+    :type value: Union[str, None]
+
+    :return: The value or ``None``.
+    :rtype: Union[str, None]
+    '''
+
+    if value is None:
+        return None
+    
+    if value.strip() == '':
+        return None
+
+    return value