public ImportedField getNestedField(String name) {
        if (name.contains(".")) {
            String superFieldName = name.substring(0,name.indexOf("."));
            String subFieldName = name.substring(name.indexOf(".")+1);
            ImportedField superField = nestedFields.get(superFieldName);
            if (superField != null && superField instanceof ImportedComplexField) {
                return ((ImportedComplexField)superField).getNestedField(subFieldName);
            }
            return null;
        }
        return nestedFields.get(name);
    }
A complex field that is imported from a concrete field in a referenced document type and given an alias name.
config-model/src/main/java/com/yahoo/schema/document/ImportedComplexField.java