def specific_keys
      %w(
        animate
        size
        background
        transparent
        enhanced
        rounded
        butt
        linewidth
        dashlength
        tiny
        small
        medium
        large
        giant
        font
        fontscale
        crop
      )
    end
def specific_keys
      %w(
        animate
        size
        background
        transparent
        enhanced
        rounded
        butt
        linewidth
        dashlength
        tiny
        small
        medium
        large
        giant
        font
        fontscale
        crop
      )
    end
This plot have some specific options which
 should be handled different way than others.
 Here are keys of this options.