public void addAlias(String from, String to) {
        verifyThat(! aliases.containsKey(to), "already has alias", to);
        aliases.put(to, from);
    }
This class holds the extracted information after parsing a
"attribute" block, using simple data structures as far as
possible.  Do not put advanced logic here!
@author arnej27959
config-model/src/main/java/com/yahoo/schema/parser/ParsedAttribute.java