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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 running_instances(self, context, process_name):
 """Get a list of running instances. Args: context (`ResolvedContext`):
 Context the process is running in. process_name (str):
 Name of the process. Returns: List of (`subprocess.Popen`, start-time) 2-tuples, where start_time is the epoch time the process was added. """

        handle = (id(context), process_name)
        it = self.processes.get(handle, {}).itervalues()
        entries = [x for x in it if x[0].poll() is None]
        return entries