```xml
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ns4:query_definition xmlns:ns2="http://www.i2b2.org/xsd/cell/crc/psm/1.1/" xmlns:ns4="http://www.i2b2.org/xsd/cell/crc/psm/querydefinition/1.1/" xmlns:ns3="http://www.i2b2.org/xsd/cell/crc/psm/analysisdefinition/1.1/">
    <query_name>Arterial HCO3 (@08:51:57</query_name>
    <query_timing>ANY</query_timing>
    <specificity_scale>0</specificity_scale>
    <panel>
        <panel_number>1</panel_number>
        <panel_timing>ANY</panel_timing>
        <panel_accuracy_scale>100</panel_accuracy_scale>
        <invert>0</invert>
        <total_item_occurrences>1</total_item_occurrences>
        <item>
            <hlevel>4</hlevel>
            <item_name>Arterial HCO3 (Group:ABASEX)</item_name>
            <item_key>\\i2b2_LABS\i2b2\Labtests\LAB\(LLB16) Chemistry\(LLB24) Blood Gases\ABASEX\</item_key>
            <item_icon>FA</item_icon>
            <tooltip>Labtests \ Chemistry \ Blood Gases \ Arterial HCO3 (Group:ABASEX)</tooltip>
            <class>ENC</class>
            <constrain_by_value>
                <value_operator>EQ</value_operator>
                <value_constraint>@</value_constraint>
                <value_type>FLAG</value_type>
            </constrain_by_value>
            <item_is_synonym>false</item_is_synonym>
        </item>
    </panel>
</ns4:query_definition>

```

I want to find all instances where the Arterial HCO3 (Group:ABASEX) lab test result has a value equal to @ in the i2b2 database, with no specific time frame constraint and a high level of accuracy (100), within a panel that contains only this single item. The query will not be inverted, and the search will return only one occurrence of the item. This query is related to the Chemistry category, specifically the Blood Gases subcategory, and is represented by the icon FA. The tooltip for this query is "Labtests \ Chemistry \ Blood Gases \ Arterial HCO3 (Group:ABASEX)". The class of the query is ENC, and it is not a synonym for another query.