code: private void obtainShowHeaderDivider(@StyleRes final int themeResourceId) {
          TypedArray typedArray = getContext().getTheme().obtainStyledAttributes(themeResourceId,
                  new int[]{R.attr.materialDialogShowHeaderDivider});
          showHeaderDivider(typedArray.getBoolean(0, true));
      }
docs: Obtains, whether the divider of the dialog's header should be shown, or not, from a specific
  theme.
  
  @param themeResourceId
  The resource id of the theme, the visibility should be obtained from, as an {@link
  Integer} value