code: def parse(type: Type):
          
  
          def decorator(parser):
              EnvVar.parsers[type] = parser
              return parser
  
          return decorator
docs: Register a parser for a attribute type.
  
          Parsers will be used to parse `str` type objects from either
          the commandline arguments or environment variables.
  
          Args:
              type: the type the decorated function will be responsible
                  for parsing a environment variable to.