def -(other)
      raise "#{self.class} cannot handle #{other.class} with the minus operator" unless other.class == Features

      self_hash = Features.hashnize(self)
      other_hash = Features.hashnize(other)

      diff_features = (self_hash.keys - other_hash.keys).map do |key|
        self_hash[key]
      end

      Features.new(diff_features)
    end
def -(other)
      raise "#{self.class} cannot handle #{other.class} with the minus operator" unless other.class == Features

      self_hash = Features.hashnize(self)
      other_hash = Features.hashnize(other)

      diff_features = (self_hash.keys - other_hash.keys).map do |key|
        self_hash[key]
      end

      Features.new(diff_features)
    end
Array<Feature>