private DocumentType findDocFromSchemas(String name) {
        var dt = documentsFromSchemas.get(name);
        if (dt == null) {
            throw new IllegalArgumentException("missing document type for: " + name);
        }
        return dt;
    }
Helper class for converting ParsedType instances to DataType

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