public SummaryField getSummaryField(String name) {
        for (DocumentSummary summary : summaries.values()) {
            SummaryField summaryField = summary.getSummaryField(name);
            if (summaryField != null) {
                return summaryField;
            }
        }
        if (inherited.isEmpty()) return null;
        return requireInherited().getSummaryField(name);
    }
Returns the first explicit instance found of a summary field with this name, or null if not present (implicitly
or explicitly) in any summary class.
config-model/src/main/java/com/yahoo/schema/Schema.java