# The processor as a filter: null means skip, not fail

input   : Product[sku=ABC-0001, name=Widget 1, priceCents=1001]
result  : Product[sku=ABC-0001, name=Widget 1, priceCents=1001]

input   : Product[sku=abc-0012, name=Widget 12, priceCents=1012]   <- lowercase sku, fails ^[A-Z]{3}-\d{4}$
result  : null

input   : Product[sku=ABC-0033, name=Widget 33, priceCents=0]   <- priceCents is zero
result  : null
