How to update avatar from SoundCloud API in ruby? -

how can update user's avatar on soundcloud?

soundcloud.new( {   :client_id => client_id,   :client_secret => client_secret,   :access_token => user.all[1].code }).put('/me', :user => {:avatar_url => file.new(rails.root.join('test.jpg').to_s, 'rb')}) 

i tried code not working. tried fields :avatar, :image