> <span class="modifier_kind"><span class="modifier"></span> <span class="kind">def</span></span> <span class="symbol"><span class="implicit">ensuring</span><span class="params">(<span name="cond">cond: (<a href="" name="provingground.induction.ExstInducStrucs.IndConsSeqExst" id="provingground.induction.ExstInducStrucs.IndConsSeqExst" class="extype">IndConsSeqExst</a>[<span name="provingground.induction.ExstInducStrucs.IndConsSeqExst.SS" class="extype">SS</span>, <span name="provingground.induction.ExstIndu