Return value of given option.

        If option isn't found - return default_value (None by default).

        Args:
        - option: string with path to option with `:` separator

def get(cls, option, default_value=None):
        """
        Return value of given option.

        If option isn't found - return default_value (None by default).

        Args:
        - option: string with path to option with `:` separator
        """
        config = cls.__get_instance()
        for name in option.split(':'):
            if not name:
                raise Exception('Incorrect value in path (maybe double `:` or empty path)')
            if name not in config:
                return default_value
            config = config[name]
        return deepcopy(config)