```ruby
module Operable
  module Fields

    extend ActiveSupport::Concern

    # Return a list of attributes (with values) to be included in operations
    #
    # Returns Hash of key (string) => value pairs
    def operable_values
      raise "Please specify one or more fields via operable_on in your model definition!" if self.class.operable_fields.nil?

      keys = attributes.keys
      keys << relations.keys if respond_to?(:associations)
      values = attributes.select {|k, v| self.class.operable_fields.include? k }
      if respond_to?(:associations)
        associations.select {|k, v| self.class.operable_fields.include? k }.each do |k, v|
          values[k.to_s] = send(k)
        end
      end

      values
    end

  end
end
```

Fix type issue on Ruby < 1.9
user
```ruby
module Operable
  module Fields

    extend ActiveSupport::Concern

    # Return a list of attributes (with values) to be included in operations
    #
    # Returns Hash of key (string) => value pairs
    def operable_values
      raise "Please specify one or more fields via operable_on in your model definition!" if self.class.operable_fields.nil?

      values = {}
      attributes.select {|k, v| self.class.operable_fields.include? k }.each do |k, v|
        values[k.to_s] = v
      end
      if respond_to?(:associations)
        associations.select {|k, v| self.class.operable_fields.include? k }.each do |k, v|
          values[k.to_s] = send(k)
        end
      end

      values
    end

  end
end
```
assistant