python
@@ -4281,7 +4281,7 @@ def _ensure(self):
         if not self.indents:
             fail('IndentStack expected indents, but none are defined.')
 
-    def measure(self, line):
+    def measure(self, line: str) -> int:
         """
         Returns the length of the line's margin.
         """
@@ -4295,7 +4295,7 @@ def measure(self, line):
             return self.indents[-1]
         return len(line) - len(stripped)
 
-    def infer(self, line):
+    def infer(self, line: str) -> int:
         """
         Infer what is now the current margin based on this line.
         Returns:
@@ -4328,19 +4328,19 @@ def infer(self, line):
         return outdent_count
 
     @property
-    def depth(self):
+    def depth(self) -> int:
         """
         Returns how many margins are currently defined.
         """
         return len(self.indents)
 
-    def indent(self, line):
+    def indent(self, line: str) -> str:
         """
         Indents a line by the currently defined margin.
         """
         return self.margin + line
 
-    def dedent(self, line):
+    def dedent(self, line: str) -> str:
         """
         Dedents a line by the currently defined margin.
         (The inverse of 'indent'.)