diff --git a/sphinx/io.py b/sphinx/io.py
index 067aa917fab..4fdcca09a04 100644
--- a/sphinx/io.py
+++ b/sphinx/io.py
@@ -143,8 +143,8 @@ def setup(self, app: Sphinx) -> None:
             if transform in self.transforms:
                 self.transforms.remove(transform)
 
-    def parse(self):
-        """Parse `self.input` into a document tree."""
+    def parse(self) -> None:
+        """Override the BaseReader parse method to call self.parser.parse_inline()."""
         self.document = document = self.new_document()
         self.parser.parse_inline(self.input, document)
         document.current_source = document.current_line = None
diff --git a/sphinx/parsers.py b/sphinx/parsers.py
index 6c6d82b2910..09ee7e8ff28 100644
--- a/sphinx/parsers.py
+++ b/sphinx/parsers.py
@@ -66,7 +66,6 @@ def get_transforms(self) -> list[type[Transform]]:
 
     def parse_inline(self, inputstring: str, document: nodes.document) -> None:
         """Parse inline syntax from text and generate a document tree."""
-
         # Avoid "Literal block expected; none found." warnings.
         has_literal = inputstring.endswith('::')
         if has_literal:
@@ -86,10 +85,9 @@ def parse_inline(self, inputstring: str, document: nodes.document) -> None:
         self.finish_parse()
         if has_literal:
             p = document[0]
-            assert(isinstance(p, nodes.paragraph))
+            assert isinstance(p, nodes.paragraph)
             p += nodes.Text(':')
 
-
     def parse(self, inputstring: str | StringList, document: nodes.document) -> None:
         """Parse text and generate a document tree."""
         self.setup_parse(inputstring, document)  # type: ignore[arg-type]
diff --git a/sphinx/transforms/i18n.py b/sphinx/transforms/i18n.py
index 70dda14cfff..1c0cf809b40 100644
--- a/sphinx/transforms/i18n.py
+++ b/sphinx/transforms/i18n.py
@@ -5,7 +5,6 @@
 import contextlib
 from os import path
 from re import DOTALL, match
-from textwrap import indent
 from typing import TYPE_CHECKING, Any, TypeVar
 
 from docutils import nodes