def symbolize_keys(hash)
      hash.inject({}) do |h, (key, value)|
        h[key.to_sym] = value.is_a?(Hash) ? symbolize_keys(value) : value
        h
      end
    end
def symbolize_keys(hash)
      hash.inject({}) do |h, (key, value)|
        h[key.to_sym] = value.is_a?(Hash) ? symbolize_keys(value) : value
        h
      end
    end
Converts all keys of a [Hash] to symbols. Performs deep conversion.

 @param [Hash] hash to convert
 @return [Hash] a copy of the original hash