def key?(key)
      configuration.key?(key.to_sym) || config_contexts.key?(key.to_sym)
    end
def key?(key)
      configuration.key?(key.to_sym) || config_contexts.key?(key.to_sym)
    end
Check if Mixlib::Config has a config option.

 === Parameters
 key<Symbol>:: The config option to check for

 === Returns
 <True>:: If the config option exists
 <False>:: If the config option does not exist