<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_duration(self, key, value):
 """Add a duration for the specified key :param str key: The value name :param float value: The value .. versionadded:: 3.19.0 """

        if key not in self.durations:
            self.durations[key] = []
        self.durations[key].append(value)