class Restforce::Middleware::Multipart

def has_multipart?(obj)
  # string is an enum in 1.8, returning list of itself
  if obj.respond_to?(:each) && !obj.is_a?(String)
    (obj.respond_to?(:values) ? obj.values : obj).each do |val|
      return true if val.respond_to?(:content_type) || has_multipart?(val)
    end
  end
  false
end