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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def increment(self, subname=None, delta=1):
        '''Increment the gauge with `delta`

        :keyword subname: The subname to report the data to (appended to the
            client name)
        :type subname: str
        :keyword delta: The delta to add to the gauge
        :type delta: int

        >>> gauge = Gauge('application_name')
        >>> gauge.increment('gauge_name', 10)
        True
        >>> gauge.increment(delta=10)
        True
        >>> gauge.increment('gauge_name')
        True
        '''
        delta = int(delta)
        sign = "+" if delta >= 0 else ""
        return self._send(subname, "%s%d" % (sign, delta))