'Returns modification time of an entry.
@return: Last modification date (seconds since epoch) of entry C{key}
@raise KeyError: Raised when there is no such key'

def getModificationTime(self, key):

    if (not (type(key) == bytes)):
        raise TypeError('DirDBM    key    must    be    bytes')
    path = self._dnamePath.child(self._encode(key))
    if path.isfile():
        return path.getModificationTime()
    else:
        raise KeyError(key)
