```ruby
require 'signal/active_record'
require 'signal/listener'
require 'signal/version'

module Signal
  def on(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def before(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def after(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def add_listener(listener)
    listeners << listener
    self
  end

  def emit(event, *args)
    emit_signal(:before, event, *args)
    emit_signal(:on, event, *args)
    emit_signal(:after, event, *args)
    nil
  end

  def listeners
    @listeners ||= []
  end

  private
  def emit_signal(type, event, *args)
    listeners.each do |listener|
      method_name = "#{type}_#{event}"

      if listener.respond_to?(method_name)
        listener.public_send(method_name, *args)
      end
    end
  end
end
```

Send messages without considering method visibility.
user
```ruby
require 'signal/active_record'
require 'signal/listener'
require 'signal/version'

module Signal
  def on(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def before(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def after(event, &block)
    listeners << Listener.new(self, __method__, event, &block)
    self
  end

  def add_listener(listener)
    listeners << listener
    self
  end

  def emit(event, *args)
    emit_signal(:before, event, *args)
    emit_signal(:on, event, *args)
    emit_signal(:after, event, *args)
    nil
  end

  def listeners
    @listeners ||= []
  end

  private
  def emit_signal(type, event, *args)
    listeners.each do |listener|
      method_name = "#{type}_#{event}"
      listener.send(method_name, *args) if listener.respond_to?(method_name)
    end
  end
end
```
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