A string of octets containing one bit per VLAN. The
first octet corresponds to VLANs with VlanIndex values
1 through 8; the second octet to VLANs 9 through
16 etc. The most significant bit of each octet
corresponds to the lowest VlanIndex value in that octet.
The set of vlans configured by management to unmap from this
Instance. A vlan may not be unmapped from this instance if
it is not already mapped to this Instance. This object is
used only for SET operation.GET Operation returns null values.