fix: resolve CI/CD test failures and linting issues

config_convert/cli.py

@@ -7,7 +7,6 @@ from typing import Optional
 import typer
 from rich.console import Console
 from rich.table import Table
-from rich.syntax import Syntax
 
 from config_convert import __version__
 from config_convert.converters import (
@@ -89,6 +88,7 @@ def convert(
                 echo_error("Please specify --from when using --stdin")
                 raise typer.Exit(2)
         else:
+            assert input_file is not None
             fmt = from_format or get_format_from_path(input_file)
             data_str = Path(input_file).read_text(encoding="utf-8")