import re


def is_valid_tn(self, tn_string):
    valid_tn = re.compile('^\d{3}-\d{3}-\d{4}$')
    return re.match(valid_tn, tn_string)


@@ -25,14 +25,8 @@
 _tn(
-self, 
 tn_s
@@ -123,9 +123,8 @@
 string)%0A
-%0A

remove requirement for self from valid phone number validator