code: public ExpectedColumn selectColumn() throws Exception
      {
          if (isNull()) return new NullColumn();
  
          if (expectFalse()) return new ExpectFalseColumn(message());
          if (expectTrue()) return new ExpectTrueColumn(message());
          if (expectNull()) return new ExpectNullColumn(message());
          if (expectNotNull()) return new ExpectNotNullColumn(message());
  
          return new ExpectedColumn(message());
      }
docs: <p>selectColumn.</p>
  
  @return a {@link Column} object.
  @throws Exception if any.