`DirFileSystem` does not delegate `write_text` and `delete`

[dAnjou]

Hi,

as far as I understand, this should not work, it should raise instead:

from fsspec import AbstractFileSystem
from fsspec.implementations.dirfs import DirFileSystem
from fsspec.implementations.memory import MemoryFileSystem

class ReadOnlyBaseFileSystem(MemoryFileSystem, AbstractFileSystem):
    def write_text(self, *_, **__):
        raise NotImplementedError

    def delete(self, *_, **__):
        raise NotImplementedError

ro_fs = ReadOnlyBaseFileSystem()
fs = DirFileSystem("foo", ro_fs)
fs.write_text("bar", "lorem ipsum")  # doesn't raise
print(ro_fs.read_text("foo/bar"))
fs.delete("bar")  # doesn't raise

$ python main.py 
lorem ipsum

🙏