Changed read_csv type hint for na_values and added tests Issue#53813 (#54486)

* Changed read_csv type hint for na_values and added tests Issue#53813

* mend

* Changed read_csv type hint for na_values and added tests Issue#53813

Author: kvn4

pandas/io/parsers/readers.py

@@ -65,6 +65,7 @@
 if TYPE_CHECKING:
     from collections.abc import (
         Hashable,
+        Iterable,
         Mapping,
         Sequence,
     )
@@ -638,8 +639,10 @@ def read_csv(
     skiprows: list[int] | int | Callable[[Hashable], bool] | None = ...,
     skipfooter: int = ...,
     nrows: int | None = ...,
-    na_values: Sequence[str] | Mapping[str, Sequence[str]] | None = ...,
-    keep_default_na: bool = ...,
+    na_values: Hashable
+    | Iterable[Hashable]
+    | Mapping[Hashable, Iterable[Hashable]]
+    | None = ...,
     na_filter: bool = ...,
     verbose: bool = ...,
     skip_blank_lines: bool = ...,
@@ -695,7 +698,10 @@ def read_csv(
     skiprows: list[int] | int | Callable[[Hashable], bool] | None = ...,
     skipfooter: int = ...,
     nrows: int | None = ...,
-    na_values: Sequence[str] | Mapping[str, Sequence[str]] | None = ...,
+    na_values: Hashable
+    | Iterable[Hashable]
+    | Mapping[Hashable, Iterable[Hashable]]
+    | None = ...,
     keep_default_na: bool = ...,
     na_filter: bool = ...,
     verbose: bool = ...,
@@ -752,7 +758,10 @@ def read_csv(
     skiprows: list[int] | int | Callable[[Hashable], bool] | None = ...,
     skipfooter: int = ...,
     nrows: int | None = ...,
-    na_values: Sequence[str] | Mapping[str, Sequence[str]] | None = ...,
+    na_values: Hashable
+    | Iterable[Hashable]
+    | Mapping[Hashable, Iterable[Hashable]]
+    | None = ...,
     keep_default_na: bool = ...,
     na_filter: bool = ...,
     verbose: bool = ...,
@@ -809,7 +818,10 @@ def read_csv(
     skiprows: list[int] | int | Callable[[Hashable], bool] | None = ...,
     skipfooter: int = ...,
     nrows: int | None = ...,
-    na_values: Sequence[str] | Mapping[str, Sequence[str]] | None = ...,
+    na_values: Hashable
+    | Iterable[Hashable]
+    | Mapping[Hashable, Iterable[Hashable]]
+    | None = ...,
     keep_default_na: bool = ...,
     na_filter: bool = ...,
     verbose: bool = ...,
@@ -879,7 +891,10 @@ def read_csv(
     skipfooter: int = 0,
     nrows: int | None = None,
     # NA and Missing Data Handling
-    na_values: Sequence[str] | Mapping[str, Sequence[str]] | None = None,
+    na_values: Hashable
+    | Iterable[Hashable]
+    | Mapping[Hashable, Iterable[Hashable]]
+    | None = None,
     keep_default_na: bool = True,
     na_filter: bool = True,
     verbose: bool = False,