code: @Nonnull
    public FineUploader5Validation setAcceptFiles (@Nullable final Collection <? extends IMimeType> aAcceptFiles)
    {
      m_aValidationAcceptFiles.setAll (aAcceptFiles);
      return this;
    }
docs: Used by the file selection dialog. Restrict the valid file types that
  appear in the selection dialog by listing valid content-type specifiers
  here. See docs on the accept attribute of the &lt;input&gt; element
  
  @param aAcceptFiles
  The MIME types to be set.
  @return this for chaining