code: def valid_arxiv_categories():
      
      schema = load_schema('elements/arxiv_categories')
      categories = schema['enum']
      categories.extend(_NEW_CATEGORIES.keys())
  
      return categories
docs: List of all arXiv categories that ever existed.
  
      Example:
          >>> from inspire_schemas.utils import valid_arxiv_categories
          >>> 'funct-an' in valid_arxiv_categories()
          True