code: protected Operation joinEqWithSourceAndAsOfCheck(Attribute other)
      {
          Mapper mapper = null;
          if (this.getSourceAttributeType() != null && !(other instanceof MappedAttribute) && this.getSourceAttributeType().equals(other.getSourceAttributeType()))
          {
              MultiEqualityMapper mem = new MultiEqualityMapper(this, other);
              mem.addAutoGeneratedAttributeMap(this.getSourceAttribute(), other.getSourceAttribute());
              mapper = mem;
          }
          mapper = constructEqualityMapperWithAsOfCheck(other, mapper);
          if (mapper == null)
          {
              mapper = this.constructEqualityMapper(other);
          }
          mapper.setAnonymous(true);
          Attribute target = other;
          if (other instanceof MappedAttribute)
          {
              target = ((MappedAttribute)other).getWrappedAttribute();
          }
          return new MappedOperation(mapper, new All(target));
      }
docs: /*
  public Operation in(List dataHolders, Extractor extractor)
  {
  return new InOperationWithExtractor(this, dataHolders, extractor);
  }