def <<(file_path)
      return self unless File.exist?(file_path)

      ext = File.extname(file_path).delete('.')

      raise Error, "The option file's extension '#{ext}' is not supported" unless self.class.supported_extensions.include?(ext)

      super(ConfigFile.const_get(ext.upcase).new(file_path))
    end
def <<(file_path)
      return self unless File.exist?(file_path)

      ext = File.extname(file_path).delete('.')

      raise Error, "The option file's extension '#{ext}' is not supported" unless self.class.supported_extensions.include?(ext)

      super(ConfigFile.const_get(ext.upcase).new(file_path))
    end
@param [ String ] file_path

 @return [ Self ]