code: public java.util.List<String> getExpressionNames() {
          if (expressionNames == null) {
              expressionNames = new com.amazonaws.internal.SdkInternalList<String>();
          }
          return expressionNames;
      }
docs: <p>
  Limits the <code><a>DescribeExpressions</a></code> response to the specified expressions. If not specified, all
  expressions are shown.
  </p>
  
  @return Limits the <code><a>DescribeExpressions</a></code> response to the specified expressions. If not
  specified, all expressions are shown.