Add missing objects to xml.etree.ElementTree (#6540)

Co-authored-by: Akuli <akuviljanen17@gmail.com>

stdlib/xml/etree/ElementTree.pyi

@@ -10,6 +10,7 @@ from typing import (
     Iterable,
     Iterator,
     KeysView,
+    Mapping,
     MutableSequence,
     Sequence,
     TypeVar,
@@ -259,11 +260,29 @@ def fromstringlist(sequence: Sequence[str | bytes], parser: XMLParser | None = .
 _ElementFactory = Callable[[Any, Dict[Any, Any]], Element]
 
 class TreeBuilder:
-    def __init__(self, element_factory: _ElementFactory | None = ...) -> None: ...
+    if sys.version_info >= (3, 8):
+        # comment_factory can take None because passing None to Comment is not an error
+        def __init__(
+            self,
+            element_factory: _ElementFactory | None = ...,
+            *,
+            comment_factory: Callable[[str | None], Element] | None = ...,
+            pi_factory: Callable[[str, str | None], Element] | None = ...,
+            insert_comments: bool = ...,
+            insert_pis: bool = ...,
+        ) -> None: ...
+        insert_comments: bool
+        insert_pis: bool
+    else:
+        def __init__(self, element_factory: _ElementFactory | None = ...) -> None: ...
     def close(self) -> Element: ...
     def data(self, __data: str | bytes) -> None: ...
     def start(self, __tag: str | bytes, __attrs: dict[str | bytes, str | bytes]) -> Element: ...
     def end(self, __tag: str | bytes) -> Element: ...
+    if sys.version_info >= (3, 8):
+        # These two methods have pos-only parameters in the C implementation
+        def comment(self, __text: str | None) -> Element: ...
+        def pi(self, __target: str, __text: str | None = ...) -> Element: ...
 
 if sys.version_info >= (3, 8):
     class C14NWriterTarget:
@@ -279,6 +298,12 @@ if sys.version_info >= (3, 8):
             exclude_attrs: Iterable[str] | None = ...,
             exclude_tags: Iterable[str] | None = ...,
         ) -> None: ...
+        def data(self, data: str) -> None: ...
+        def start_ns(self, prefix: str, uri: str) -> None: ...
+        def start(self, tag: str, attrs: Mapping[str, str]) -> None: ...
+        def end(self, tag: str) -> None: ...
+        def comment(self, text: str) -> None: ...
+        def pi(self, target: str, data: str) -> None: ...
 
 class XMLParser:
     parser: Any