Update CPU stats using the input method.

def update(self):
        """Update CPU stats using the input method."""

        # Grab stats into self.stats
        if self.input_method == 'local':
            stats = self.update_local()
        elif self.input_method == 'snmp':
            stats = self.update_snmp()
        else:
            stats = self.get_init_value()

        # Update the stats
        self.stats = stats

        return self.stats