Getting Error when access Item Attribute group EFF field value in Order Management Extension

Summary:

we need to access this Customer Number field under Manage item —>Specifications—→MAC_FINISH_GOODS_BARE in OM Extensions ,i've tried the code but i'm getting error.

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):

import oracle.apps.scm.doo.common.extensions.ValidationException;
import oracle.apps.scm.doo.common.extensions.Message;
import java.util.logging.Level;

def lines = header.getAttribute("Lines");

def HeaderId =header.getAttribute("HeaderId");
while (lines.hasNext()) {
def line = lines.next();
def InvItemId = line.getAttribute("ProductIdentifier");