code: def matchesTripleExprRef(cntxt: Context, T: RDFGraph, expr: ShExJ.tripleExprLabel, _: DebugContext) -> bool:
      
      expr = cntxt.tripleExprFor(expr)
      if expr is None:
          cntxt.fail_reason = "{expr}: Reference not found"
          return False
      return matchesExpr(cntxt, T, expr)
docs: expr is an tripleExprRef and satisfies(value, tripleExprWithId(tripleExprRef), G, m).
      The tripleExprWithId function is defined in Triple Expression Reference Requirement below.