code: public static QueryColumn toQueryColumn(Object o, PageContext pc) throws PageException {
  	if (o instanceof QueryColumn) return (QueryColumn) o;
  	if (o instanceof String) {
  	    o = VariableInterpreter.getVariableAsCollection(pc, (String) o);
  	    if (o instanceof QueryColumn) return (QueryColumn) o;
  	}
  
  	throw new CasterException(o, "querycolumn");
      }
docs: converts a object to a QueryColumn, if possible, also variable declarations are allowed. this
  method is used within the generated bytecode
  
  @param o
  @return
  @throws PageException
  @info used in bytecode generation