ENH: Add annotations for PytestTester

Author: Bas van Beek

numpy/_pytesttester.pyi

@@ -0,0 +1,18 @@
+from typing import List, Iterable
+from typing_extensions import Literal as L
+
+__all__: List[str]
+
+class PytestTester:
+    module_name: str
+    def __init__(self, module_name: str) -> None: ...
+    def __call__(
+        self,
+        label: L["fast", "full"] = ...,
+        verbose: int = ...,
+        extra_argv: None | Iterable[str] = ...,
+        doctests: L[False] = ...,
+        coverage: bool = ...,
+        durations: int = ...,
+        tests: None | Iterable[str] = ...,
+    ) -> bool: ...