def update(other_hash)
      other_hash.each_pair { |key, value| regular_writer(convert_key(key), convert_value(value)) }
      self
    end
def update(other_hash)
      other_hash.each_pair { |key, value| regular_writer(convert_key(key), convert_value(value)) }
      self
    end
Updates the instantized hash with values from the second:

   hash_1 = HashWithIndifferentAccess.new
   hash_1[:key] = "value"

   hash_2 = HashWithIndifferentAccess.new
   hash_2[:key] = "New Value!"

   hash_1.update(hash_2) # => {"key"=>"New Value!"}