def x_ticks(self, *ticks):
if ticks:<EOL><INDENT>for tick in ticks:<EOL><INDENT>if not is_numeric(tick):<EOL><INDENT>raise TypeError("<STR_LIT>" % str(tick))<EOL><DEDENT><DEDENT>self._x_ticks = tuple(sorted(ticks))<EOL><DEDENT>else:<EOL><INDENT>if self._x_ticks:<EOL><INDENT>return self._x_ticks<EOL><DEDENT>else:<EOL><INDENT>return determine_ticks(self.x_lower_limit(), self.x_upper_limit())<EOL><DEDENT><DEDENT>
The points on the x-axis for which there are markers and grid lines.

        There are default ticks, but you can pass values to this method to
        override the defaults. Otherwise the method will return the ticks.

        :param \*ticks: if given, these will be chart's x-ticks.
        :rtype: ``tuple``