```ruby
module Metrics
  module Rails
    class Group
      
      def initialize(prefix)
        @prefix = "#{prefix}."
      end
      
      def group(prefix)
        prefix = @prefix + prefix
        yield self.class.new(prefix)
      end
      
      def increment(counter, by=1)
        counter = @prefix + counter
        Metrics::Rails.increment counter, by
      end
      
      def measure(event, duration)
        event = @prefix + event
        Metrics::Rails.measure event, duration
      end
      alias :timing :measure
      
    end
  end
end```

Improve handling of non-strings with Group methods.
user
```ruby
module Metrics
  module Rails
    class Group
      
      def initialize(prefix)
        @prefix = "#{prefix}."
      end
      
      def group(prefix)
        prefix = "#{@prefix}#{prefix}"
        yield self.class.new(prefix)
      end
      
      def increment(counter, by=1)
        counter = "#{@prefix}#{counter}"
        Metrics::Rails.increment counter, by
      end
      
      def measure(event, duration)
        event = "#{@prefix}#{event}"
        Metrics::Rails.measure event, duration
      end
      alias :timing :measure
      
    end
  end
end```
assistant