public static String snakeToPascalCase(String str) {
        return toCamelCase(str, true, '_');
    }
<p>Converts all words separated by "_" into PascalCase, that is each
word is made up of a titlecase character and then a series of
lowercase characters.</p>

<p>PacalCase is just like CamelCase, except the first character is an
uppercase letter.</p>

@param str  the String to be converted to PascalCase, may be null
@return camelCase of String, <code>null</code> if null String input
smithy-utils/src/main/java/software/amazon/smithy/utils/CaseUtils.java