def retrieve_command(command_to_run)
      if command_map.has_key?(command_to_run)
        command_map[command_to_run]
      else
        command = nil
        category_command_map.each do |category, commands|
          command = commands[command_to_run] if commands.has_key?(command_to_run)
        end
        # return the command, or nil if it wasn't found
        command
      end
    end
def retrieve_command(command_to_run)
      if command_map.has_key?(command_to_run)
        command_map[command_to_run]
      else
        command = nil
        category_command_map.each do |category, commands|
          command = commands[command_to_run] if commands.has_key?(command_to_run)
        end
        # return the command, or nil if it wasn't found
        command
      end
    end
retrieves the commmand from either the command_map
 or the category_command_map, if the command is not found
 return nil