BI Publisher: Handling NULL XML Value

There will be three possible scenarios for the value of an element in a XML data, 

1. XML tag value present in the XML data, and it has a value which is not NULL
for ex:
<PO_NUMBER>123</PO_NUMBER>

Suppose you want to give some condition to check not null similar to the one we give in PL/SQL as,
IF value IS NOT NULL THEN
---
---
END IF;
BI Publisher syntax for this is,

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