public String[] getPossibleValues(String name) {
    EnvironmentVariableHandler handler = getAppropriateHandler(name);
    if (handler == null)
      return null;

    EnvironmentVariableSpecs.Spec spec = handler.getSpecs().getSpec(name);
    return spec == null ? null : spec.getPossibleValues();
  }
Gets all possible valid values of an environment variable.
@param name environment variable name
@return An array of all possible valid values of the environment variable. Returns null
if the environment variable name given is invalid.
samza-sql-shell/src/main/java/org/apache/samza/sql/client/cli/CliEnvironment.java