code: public TupleExpression getTupleExpression() {
          Expression leftExpression = this.getLeftExpression();
  
          return leftExpression instanceof TupleExpression
                      ? (TupleExpression) leftExpression
                      : null;
      }
docs: This method returns the left hand side of the declaration cast to the TupleExpression type.
  This is an unsafe method to call. In a single assignment statement, the left hand side will
  be a VariableExpression and a ClassCastException will occur. If you invoke this method then
  be sure to invoke isMultipleAssignmentDeclaration() first to check that it is safe to do so.
  If that method returns true then this method is safe to call.
  @return
  left hand side of multiple assignment declarations
  @throws ClassCastException
  if the left hand side is not a TupleExpression (and is probably a VariableExpression).