def valid_page_name(page):
    """
    Checks for valid mainspace Wikipedia page name

    Args:
        page: The page name to validate

    Returns:
        True if `page` is valid, False otherwise
    """
    NON_MAINSPACE = ['File:',
                     'File talk:',
                     'Wikipedia:',
                     'Wikipedia talk:',
                     'Project:',
                     'Project talk:',
                     'Portal:',
                     'Portal talk:',
                     'Special:',
                     'Help:',
                     'Help talk:',
                     'Template:',
                     'Template talk:',
                     'Talk:',
                     'Category:',
                     'Category talk:']
    return all(not page.startswith(non_main) for non_main in NON_MAINSPACE)