} else {
data = (Instances)source;
}
// can we handle the data?
capabilities.testWithFail(data);
// prune any instances that don't contain the requested items (if any)
// can only do this if we are not reading the data incrementally
if (m_transactionsMustContain.length() > 0 && (source instanceof Instances)) {
data = parseTransactionsMustContain(data);