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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 hook(self, debug, pid):
 """ Installs the API hook on a given process and module. @warning: Do not call from an API hook callback. @type debug: L{Debug} @param debug: Debug object. @type pid: int @param pid: Process ID. """

        label = "%s!%s" % (self.__modName, self.__procName)
        try:
            hook = self.__hook[pid]
        except KeyError:
            try:
                aProcess = debug.system.get_process(pid)
            except KeyError:
                aProcess = Process(pid)
            hook = Hook(self.__preCB, self.__postCB,
                        self.__paramCount, self.__signature,
                        aProcess.get_arch() )
            self.__hook[pid] = hook
        hook.hook(debug, pid, label)