docs: def get_available_references(self, datas):
          """
          Get available manifest reference names.
  
          Every rules starting with prefix from ``nomenclature.RULE_REFERENCE``
          are available references.
  
          Only name validation is performed on these references.
  
          Arguments:
              datas (dict): Data where to search for reference declarations.
  
          Returns:
              list: List of every available reference names. This is the real
                  name unprefixed.
          """
          names = []
  
          for k, v in datas.items():
              if k.startswith(RULE_REFERENCE):
                  names.append(k[len(RULE_REFERENCE)+1:])
  
          return names