def linewidth(self, linewidth=None):
        """Returns or sets (if a value is provided) the width of the series'
        line.

        :param Number linewidth: If given, the series' linewidth will be set to\
        this.
        :rtype: ``Number``"""

        if linewidth is None:
            return self._linewidth
        else:
            if not is_numeric(linewidth):
                raise TypeError(
                 "linewidth must be number, not '%s'" % str(linewidth)
                )
            self._linewidth = linewidth