code: def is_valid_ipv6_prefix(ipv6_prefix):
      
  
      # Validate input type
      if not isinstance(ipv6_prefix, str):
          return False
  
      tokens = ipv6_prefix.split('/')
      if len(tokens) != 2:
          return False
  
      # Validate address/mask and return
      return is_valid_ipv6(tokens[0]) and is_valid_ip_prefix(tokens[1], 128)
docs: Returns True if given `ipv6_prefix` is a valid IPv6 prefix.