Mark stub-only private symbols as @type_check_only in third-party stubs (#14545)

stubs/seaborn/seaborn/distributions.pyi

@@ -1,5 +1,5 @@
 from collections.abc import Iterable
-from typing import Any, Literal, Protocol, TypeVar
+from typing import Any, Literal, Protocol, TypeVar, type_check_only
 from typing_extensions import TypeAlias, deprecated
 
 from matplotlib.axes import Axes
@@ -17,6 +17,7 @@ __all__ = ["displot", "histplot", "kdeplot", "ecdfplot", "rugplot", "distplot"]
 _T = TypeVar("_T")
 _OneOrPair: TypeAlias = _T | tuple[_T, _T]
 
+@type_check_only
 class _Fit(Protocol):
     def fit(self, a: ArrayLike) -> tuple[ArrayLike, ...]: ...
     def pdf(self, x: ArrayLike, *params: ArrayLike) -> ArrayLike: ...

stubs/seaborn/seaborn/external/kde.pyi

@@ -1,5 +1,5 @@
 from collections.abc import Callable
-from typing import Any, Literal, Protocol
+from typing import Any, Literal, Protocol, type_check_only
 from typing_extensions import TypeAlias
 
 import numpy as np
@@ -9,6 +9,7 @@ __all__ = ["gaussian_kde"]
 
 # define a "Gaussian KDE" protocol so that we can also pass `scipy.stats.gaussian_kde` to
 # functions that expect it without adding a dependency on scipy
+@type_check_only
 class _GaussianKDELike(Protocol):
     dataset: NDArray[np.float64]
     def __init__(self, dataset: ArrayLike, bw_method: Any | None = ..., weights: ArrayLike | None = ...) -> None: ...