Pushes a processor onto the processor stack.  Processors are
        objects with proc_request(), proc_response(), and/or
        proc_exception() methods, which can intercept requests,
        responses, and exceptions.  When a method invokes the send()
        method on a request, the proc_request() method on each
        processor is called in turn.  Likewise, responses are
        processed by the proc_response() method of each processor, in
        the reverse order of the calls to proc_request().  The
        proc_exception() methods are called if an exception is raised
        instead of a response being returned.

        Note that this method can append a processor to the stack, if
        the index parameter is None (the default), or a processor may
        be inserted into the stack by specifying an integer index.

        For more information about processors, see the
        requiem.Processor class.

def _push_processor(self, proc, index=None):
        """
        Pushes a processor onto the processor stack.  Processors are
        objects with proc_request(), proc_response(), and/or
        proc_exception() methods, which can intercept requests,
        responses, and exceptions.  When a method invokes the send()
        method on a request, the proc_request() method on each
        processor is called in turn.  Likewise, responses are
        processed by the proc_response() method of each processor, in
        the reverse order of the calls to proc_request().  The
        proc_exception() methods are called if an exception is raised
        instead of a response being returned.

        Note that this method can append a processor to the stack, if
        the index parameter is None (the default), or a processor may
        be inserted into the stack by specifying an integer index.

        For more information about processors, see the
        requiem.Processor class.
        """

        if index is None:
            self._procstack.append(proc)
        else:
            self._procstack.insert(index, proc)