code: public JBBPDslBuilder CustomArray(final String type, final String name, final String sizeExpression, final String param) {
      final ItemCustom item = new ItemCustom(type, name, this.byteOrder);
      item.array = true;
      item.bitLenExpression = param == null ? null : assertExpressionChars(param);
      item.sizeExpression = assertExpressionChars(sizeExpression);
      this.addItem(item);
      return this;
    }
docs: Create named custom type array which size calculated by expression.
  
  @param type           custom type, must not be null
  @param name           name of the array, can be null for anonymous one
  @param sizeExpression expression to calculate array length, must not be null.
  @param param          optional parameter for the field, can be null
  @return the builder instance, must not be null