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That line is called the "heat exchanger" and is not one line but actually 2, a very small "capillary tube" and a 1/4" or 5/16" OD "suction line".
Those 2 lines are soldered together at the factory. Over time the solder holding them together can break down and allow the lines to separate. When they do, frosting will appear on the larger suction line.
It is not possible to resolder those lines with refrigerant still in them so there is a repair kit available (see the following link) to remedy such a problem without tapping into the refrigeration system. The kit comes with instructions so the fix can be done by most fairly handy persons.
LINK > Refrigerator Heat Exchanger Repair Kit
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