class I18n::Backend::Transliterator::HashTransliterator

rule.
A transliterator which accepts a Hash of characters as its translation

def add(hash)

Add transliteration rules to the approximations hash. 
def add(hash)
  hash.keys.each do |key|
    utf8_key = key.to_s.dup.force_encoding('UTF-8')
    hash[utf8_key] = hash.delete(key).to_s
  end
  approximations.merge! hash
end

def approximations 

def approximations
  @approximations ||= {}
end

def initialize(rule = nil) 

def initialize(rule = nil)
  @rule = rule
  add DEFAULT_APPROXIMATIONS.dup
  add rule if rule
end

def transliterate(string, replacement = nil) 

def transliterate(string, replacement = nil)
  string.gsub(/[^\x00-\x7f]/u) do |char|
    approximations[char] || replacement || DEFAULT_REPLACEMENT_CHAR
  end
end