Add a few docstrings to hooks classes and implement Hook.__bool__

mypy/hooks.py

@@ -73,6 +73,9 @@ def locate(path: str) -> Optional[object]:
 
 
 class Hook(Generic[T]):
+    """
+    Holds a single hook function and its options dictionary
+    """
 
     def __init__(self) -> None:
         self.func = None  # type: T
@@ -87,6 +90,9 @@ def __ne__(self, other: object) -> bool:
     def __repr__(self) -> str:
         return 'Hook({}, {})'.format(self.func, self.options)
 
+    def __bool__(self) -> bool:
+        return self.func is not None
+
 
 # The docstring_parser hook is called for each unannotated function that has a
 # docstring. The callable should accept four arguments:
@@ -108,6 +114,10 @@ def __repr__(self) -> str:
 
 
 class Hooks:
+    """
+    Holds all known hooks
+    """
+
     def __init__(self) -> None:
         self.docstring_parser = DocstringParserHook()