code: public JBBPTextWriter SetTabSpaces(final int numberOfSpacesPerTab) {
      if (numberOfSpacesPerTab <= 0) {
        throw new IllegalArgumentException("Tab must contains positive number of space chars [" + numberOfSpacesPerTab + ']');
      }
      final int currentIdentSteps = this.indent / this.spacesInTab;
      this.spacesInTab = numberOfSpacesPerTab;
      this.indent = currentIdentSteps * this.spacesInTab;
      return this;
    }
docs: Set number of spaces per tab.
  
  @param numberOfSpacesPerTab number of spaces, must be greater than zero
  @return the context