public Builder put(String reservedWord, String conversion) {
            mappings.put(reservedWord, conversion);
            return this;
        }
Add a new reserved words.

@param reservedWord Reserved word to convert.
@param conversion Word to convert to.
@return Returns the builder.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/MappedReservedWords.java