singularize("-ous") return wrong result.

[americano212]

The singularize function causes many exceptions.
Words that end in "-ous" are usually adjectives, and most of the time they are not plural.
However, there is no way to handle the exception cleanly.

It seems bad to call '_irregular', which is a private function like this.

def add_singularize_irregular(SINGULARIZE_IGNORE: set[str]) -> None:
    for ignore_singularize in SINGULARIZE_IGNORE:
        _irregular(ignore_singularize, ignore_singularize)

SINGULARIZE_IGNORE = {
    'ambitious',
    'ovious',
    'dangerous'
}