docs: def get_variables(self) -> Set[str]:
          """Find all the variables specified in a format string.
  
          This returns a list of all the different variables specified in a format string,
          that is the variables inside the braces.
  
          """
          variables = set()
          for cmd in self._cmd:
              for var in self.__formatter.parse(cmd):
                  logger.debug("Checking variable: %s", var)
                  # creates and requires are special class values
                  if var[1] is not None and var[1] not in ["creates", "requires"]:
                      variables.add(var[1])
          return variables