allow visitor dispatch methods in pylint

pylintrc

@@ -96,7 +96,7 @@ class-rgx=[A-Z_][a-zA-Z0-9]+$
 function-rgx=[a-z_][a-z0-9_]{2,30}$
 
 # Regular expression which should only match correct method names
-method-rgx=[a-z_][a-z0-9_]{2,30}$
+method-rgx=[a-z_][a-z0-9_]{2,30}|visit_[A-Za-z]+$
 
 # Regular expression which should only match correct instance attribute names
 attr-rgx=[a-z_][a-z0-9_]{2,30}$