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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 spawn(self, process):
 """Spawn a process. Spawning a process binds it to this context and assigns the process a pid which is returned. The process' ``initialize`` method is called. Note: A process cannot send messages until it is bound to a context. :param process: The process to bind to this context. :type process: :class:`Process` :return: The pid of the process. :rtype: :class:`PID` """

    self._assert_started()
    process.bind(self)
    self.http.mount_process(process)
    self._processes[process.pid] = process
    process.initialize()
    return process.pid