How to determine package that has depencency when ts.check callback function is called?

I'm using ts.check to determine if a subset of packages from a CentOS
distribution has any unsatisfied dependencies.  In the ts.check callback
function I do a allts.dbMatch call to find out what package provides the
dependency handed to the callback.  allts is a transaction set that uses the rpm
database from the rpmbd-CentOS package, which contains all the packages in the
distribution.  This approach works great for catching any missing packages in my
subset of packages.

My question though, is how can I determine which package is the source of the
dependency that was handed to the ts.check callback?  Am I missing something or
is this just an omission on the part of the python binding?

def checkCallback(ts, depType, depName, depEVR, senseFlags):
    if depType == rpm.RPMTAG_REQUIRENAME:
        prevHdrName = ""
        newPkg = None
        if depName[0] == "/":
            dbIndex = "basenames"
        else:
            dbIndex = "providename"

        for hdr in allts.dbMatch(dbIndex, depName):
            hdrName = hdr[rpm.RPMTAG_NAME]
            # If this package has a shorter name use it so that shortest name wins
            if prevHdrName == "" or len(hdrName) < len(prevHdrName):
                prevHdrName = hdrName
                newPkg = hdr
        if newPkg:
            ts.addInstall(newPkg, newPkg, "i")
            return -1
    return 1