def from_file(
        self,
        filename: str | os.PathLike[str],
        load: t.Callable[[t.IO[t.Any]], t.Mapping[str, t.Any]],
        silent: bool = False,
        text: bool = True,
    ) -> bool:
        """Update the values in the config from a file that is loaded
        using the ``load`` parameter. The loaded data is passed to the
        :meth:`from_mapping` method.

        .. code-block:: python

            import json
            app.config.from_file("config.json", load=json.load)

            import tomllib
            app.config.from_file("config.toml", load=tomllib.load, text=False)

        :param filename: The path to the data file. This can be an
            absolute path or relative to the config root path.
        :param load: A callable that takes a file handle and returns a
            mapping of loaded data from the file.
        :type load: ``Callable[[Reader], Mapping]`` where ``Reader``
            implements a ``read`` method.
        :param silent: Ignore the file if it doesn't exist.
        :param text: Open the file in text or binary mode.
        :return: ``True`` if the file was loaded successfully.

        .. versionchanged:: 2.3
            The ``text`` parameter was added.

        .. versionadded:: 2.0
        """
        filename = os.path.join(self.root_path, filename)

        try:
            with open(filename, "r" if text else "rb") as f:
                obj = load(f)
        except OSError as e:
            if silent and e.errno in (errno.ENOENT, errno.EISDIR):
                return False

            e.strerror = f"Unable to load configuration file ({e.strerror})"
            raise

        return self.from_mapping(obj)
Update the values in the config from a file that is loaded
        using the ``load`` parameter. The loaded data is passed to the
        :meth:`from_mapping` method.

        .. code-block:: python

            import json
            app.config.from_file("config.json", load=json.load)

            import tomllib
            app.config.from_file("config.toml", load=tomllib.load, text=False)

        :param filename: The path to the data file. This can be an
            absolute path or relative to the config root path.
        :param load: A callable that takes a file handle and returns a
            mapping of loaded data from the file.
        :type load: ``Callable[[Reader], Mapping]`` where ``Reader``
            implements a ``read`` method.
        :param silent: Ignore the file if it doesn't exist.
        :param text: Open the file in text or binary mode.
        :return: ``True`` if the file was loaded successfully.

        .. versionchanged:: 2.3
            The ``text`` parameter was added.

        .. versionadded:: 2.0
        
src/flask/config.py