code: public List<BtrpOperand> getImportables(String ns) {
          List<BtrpOperand> importable = new ArrayList<>();
          for (String symbol : getExported()) {
              if (canImport(symbol, ns)) {
                  importable.add(getImportable(symbol, ns));
              }
          }
          return importable;
      }
docs: Get all the operand a given script can import
  
  @param ns the script namespace
  @return a list of importable operand, may be empty