code: public boolean equalsPositional(Object obj) {
  		if (this == obj)
  			return true;
  		if (obj == null)
  			return false;
  		if (getClass() != obj.getClass())
  			return false;
  		ResidueNumber other = (ResidueNumber) obj;
  		if (insCode == null) {
  			if (other.insCode != null)
  				return false;
  		} else if (!insCode.equals(other.insCode))
  			return false;
  		if (seqNum == null) {
  			if (other.seqNum != null)
  				return false;
  		} else if (!seqNum.equals(other.seqNum))
  			return false;
  
  		return true;
  
  	}
docs: Check if the seqNum and insertion code are equivalent,
  ignoring the chain
  @param obj
  @return