code: def get_occurrence(exchange_id, instance_index, format=u"Default"):
    
  
    root = M.GetItem(
      M.ItemShape(
        T.BaseShape(format)
      ),
      M.ItemIds()
    )
  
    items_node = root.xpath("//m:ItemIds", namespaces=NAMESPACES)[0]
    for index in instance_index:
      items_node.append(T.OccurrenceItemId(RecurringMasterId=exchange_id, InstanceIndex=str(index)))
    return root
docs: Requests one or more calendar items from the store matching the master & index.
  
      exchange_id is the id for the master event in the Exchange store.
  
      format controls how much data you get back from Exchange. Full docs are here, but acceptible values
      are IdOnly, Default, and AllProperties.
  
      GetItem Doc:
      http://msdn.microsoft.com/en-us/library/aa564509(v=exchg.140).aspx
      OccurrenceItemId Doc:
      http://msdn.microsoft.com/en-us/library/office/aa580744(v=exchg.150).aspx
  
      <m:GetItem  xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
              xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types">
        <m:ItemShape>
            <t:BaseShape>{format}</t:BaseShape>
        </m:ItemShape>
        <m:ItemIds>
          {% for index in instance_index %}
            <t:OccurrenceItemId RecurringMasterId="{exchange_id}" InstanceIndex="{{ index }}"/>
          {% endfor %}
        </m:ItemIds>
      </m:GetItem>