def ensure_binary_encoding(string)
      raise ArgumentError, "String is missing" if !string
      if string.encoding == Encoding::BINARY
        string
      else
        string.b
      end
    end
def ensure_binary_encoding(string)
      raise ArgumentError, "String is missing" if !string
      if string.encoding == Encoding::BINARY
        string
      else
        string.b
      end
    end
Returns string as-is if it is already encoded in binary encoding (aka BINARY or ASCII-8BIT).
 If it is not, converts to binary by calling stdlib's method #b.