class Hash

def deep_merge!(data)
  merge!(data, &MERGER)
end unless Hash.method_defined?(:deep_merge!)

def deep_symbolize_keys
  inject({}) { |result, (key, value)|
    value = value.deep_symbolize_keys if value.is_a?(Hash)
    result[(key.to_sym rescue key) || key] = value
    result
  }
end unless Hash.method_defined?(:deep_symbolize_keys)

def except(*less_keys)
  slice(*keys - less_keys)
end unless Hash.method_defined?(:except)

def slice(*keep_keys)
  h = {}
  keep_keys.each { |key| h[key] = fetch(key) }
  h
end unless Hash.method_defined?(:slice)