code: public JBBPDslBuilder BitArray(final JBBPBitNumber bits, final String sizeExpression) {
      return this.BitArray(null, bits, assertExpressionChars(sizeExpression));
    }
docs: Add anonymous bit array with size calculated through expression.
  
  @param bits           length of the field, must not be null
  @param sizeExpression expression to be used to calculate array size, must not be null
  @return the builder instance, must not be null