class ActiveSupport::OrderedHash

with other implementations.
ActiveSupport::OrderedHash is namespaced to prevent conflicts
when loading from yaml.
(See yaml.org/type/omap.html) to support ordered items
Also, maps the omap feature for YAML files
oh.keys # => [:a, :b], this order is guaranteed<br>oh = 2<br>oh = 1
oh = ActiveSupport::OrderedHash.new
insertion order.
ActiveSupport::OrderedHash implements a hash that preserves

def encode_with(coder) 

def encode_with(coder)
  coder.represent_seq '!omap', map { |k,v| { k => v } }
end

def extractable_options?

Returns true to make sure that this hash is extractable via Array#extract_options! 
def extractable_options?
  true
end

def nested_under_indifferent_access 

def nested_under_indifferent_access
  self
end

def reject(*args, &block) 

def reject(*args, &block)
  dup.tap { |hash| hash.reject!(*args, &block) }
end

def select(*args, &block) 

def select(*args, &block)
  dup.tap { |hash| hash.select!(*args, &block) }
end

def to_yaml_type 

def to_yaml_type
  "!tag:yaml.org,2002:omap"
end