@staticmethod
def rgb_to_ansi(color):
    """
        Converts hex RGB to the 6x6x6 xterm color space

        Args:
            color (str): RGB color string in the format "#RRGGBB"

        Returns:
            str: ansi color string in the format "ansi_n", where n
                is between 16 and 230

        Reference:
            https://github.com/chadj2/bash-ui/blob/master/COLORS.md
        """
    if color[0] != '#' or len(color) != 7:
        return None
    try:
        r = round(int(color[1:3], 16) / 51.0)
        g = round(int(color[3:5], 16) / 51.0)
        b = round(int(color[5:7], 16) / 51.0)
        n = int(36 * r + 6 * g + b + 16)
        return 'ansi_{0:d}'.format(n)
    except ValueError:
        return None
