public void addField(ParsedField field) {
        String fieldName = field.name();
        verifyThat(! extraFields.containsKey(fieldName), "already has field", fieldName);
        extraFields.put(fieldName, field);
    }
This class holds the extracted information after parsing
one schema (.sd) file, using simple data structures
as far as possible.

Do not put complicated logic here!

@author arnej27959
config-model/src/main/java/com/yahoo/schema/parser/ParsedSchema.java