Kotlin explicit backing fields

<div class="r2 backing" data-step="0"><div class="r2-head">EXPLICIT BACKING FIELD<span class="r2-live"></span></div><div class="r2-stage"><div class="r2-field-top">public <strong>List</strong><span>read only</span></div><div class="r2-field-wire"></div><div class="r2-field-bottom">field <strong>ArrayList</strong><span>mutable</span></div><div class="r2-field-action">add(item)</div></div><div class="r2-foot"><span class="r2-caption"></span><span class="r2-progress"></span></div></div>

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