Added an is_overload method in the function class(parser.py).

Added an if statement so that the D103 error will not trigger when decorated with @overload(checker.py)

Added some tests to see that it's working correctly.

src/pydocstyle/checker.py

@@ -3,7 +3,6 @@
 import ast
 import string
 import sys
-import textwrap
 import tokenize as tk
 from itertools import takewhile, chain
 from re import compile as re

src/tests/test_cases/test.py

@@ -56,13 +56,13 @@ def nested():
 
 
 @overload
-def overloaded_func(a: str) -> str:
+def overloaded_func(a: int) -> str:
     return 2
 
 
-@expect('D103: Missing docstring in public function', arg_count=1)
-def overloaded_func(a):
-    return str(a)
+@overload
+def overloaded_func(a: str) -> str:
+    return '1'
 
 
 def overloaded_func(a):