code: def _splice_index(*key):
      
      if isinstance(key[0], str):
          result = rx_index.search(key[0])
          if result:
              return tuple([result.group(1), int(result.group(2))] + list(key[1:]))
      return key
docs: Utility for key management in dig/dug
  
      If first elem of key list contains an index[], spread it out as a second
      numeric index.
  
      >>> _splice_index('abc[0]', 'def')
      ('abc', 0, 'def')
      >>> _splice_index('abc[a]', 'def')
      ('abc[a]', 'def')
      >>> _splice_index('abc[200]', 'def')
      ('abc', 200, 'def')
      >>> _splice_index('abc', 'def')
      ('abc', 'def')
      >>> _splice_index(0, 'abc', 'def')
      (0, 'abc', 'def')