public String expectOneOf(String... validValues) {
        return expectOneOf(Arrays.asList(validValues));
    }
Gets the string if it is one of the provided valid strings.

@param validValues A list of valid string values.
@return The string value.
@throws ExpectationNotMetException when the value is not one of the
 valid strings.
smithy-model/src/main/java/software/amazon/smithy/model/node/StringNode.java