const_defined?

# File actionpack/lib/action_dispatch/http/mime_type.rb, line 62
    def const_defined?(sym, inherit = true)
      ext = sym.downcase
      if Mime[ext]
        ActiveSupport::Deprecation.warn(          Accessing mime types via constants is deprecated.          Please change `Mime.const_defined?(#{sym})` to `Mime[:#{ext}]`..squish)
        true
      else
        super
      end
    end