} else {
throw new IllegalArgumentException(
"Cannot materialize non-readable input collection: " + ic);
}
} else if (impl instanceof InputTable) {
InputTable it = (InputTable) impl;
if (it.getSource() instanceof ReadableSource) {
return (ReadableSource) it.getSource();
} else {
throw new IllegalArgumentException(
"Cannot materialize non-readable input table: " + it);
}
}