class Object

def is_haml?

it's a good idea to define \{#is\_haml?} for all objects.
Because `ActionView` helpers may be included in non-`ActionView::Base` classes,
is a proper Haml context.
to determine whether or not the current context object
which call an \{#is\_haml?} method
Haml overrides various `ActionView` helpers, 
def is_haml?
  false
end