diff --git a/lynse/core_components/fields_cache/expression_parse.py b/lynse/core_components/fields_cache/expression_parse.py
index 1f729c6..5ceed09 100644
--- a/lynse/core_components/fields_cache/expression_parse.py
+++ b/lynse/core_components/fields_cache/expression_parse.py
@@ -200,7 +200,7 @@ def parse_number(value):
 
 
 class ExpressionParser:
-    """
+    r"""
     FieldExpression is a string parser used to parse field expressions. 
 
     It can reassemble the parsing result into a Filter object of LynseDB, which can filter the query result.