unregister

# File actionpack/lib/action_dispatch/http/mime_type.rb, line 216
      def unregister(symbol)
        symbol = symbol.downcase
        if mime = Mime[symbol]
          SET.delete_if { |v| v.eql?(mime) }
          LOOKUP.delete_if { |_, v| v.eql?(mime) }
          EXTENSION_LOOKUP.delete_if { |_, v| v.eql?(mime) }
        end
      end