Add one more docstring

Author: rocky

uncompyle6/scanner.py

@@ -605,6 +605,10 @@ def setTokenClass(self, tokenClass: Token) -> Token:
 
 
 def get_scanner(version: Union[str, tuple], is_pypy=False, show_asm=None) -> Scanner:
+    """
+    Import the right scanner module for ``version`` and return the Scanner class
+    in that module.
+    """
     # If version is a string, turn that into the corresponding float.
     if isinstance(version, str):
         if version not in canonic_python_version: