'Return the main IMDb URL for the given Movie, Person,
Character or Company object, or None if unable to get it.'

def get_imdbURL(self, mop):

    imdbID = self.get_imdbID(mop)
    if (imdbID is None):
        return None
    if isinstance(mop, Movie.Movie):
        url_firstPart = imdbURL_movie_main
    elif isinstance(mop, Person.Person):
        url_firstPart = imdbURL_person_main
    elif isinstance(mop, Character.Character):
        url_firstPart = imdbURL_character_main
    elif isinstance(mop, Company.Company):
        url_firstPart = imdbURL_company_main
    else:
        raise IMDbError((('object    ' + repr(mop)) + '    is    not    a    Movie,    Person,    Character    or    Company    instance'))
    return (url_firstPart % imdbID)
