def x_label(self, x_label=None):
if x_label is None:<EOL><INDENT>return self._x_label<EOL><DEDENT>else:<EOL><INDENT>if not isinstance(x_label, str):<EOL><INDENT>raise TypeError("<STR_LIT>" % str(x_label))<EOL><DEDENT>self._x_label = x_label<EOL><DEDENT>
Returns or sets (if a value is provided) the chart's x-axis label.

        :param str x_label: If given, the chart's x_label will be set to this.
        :rtype: ``str``