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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 from_scf_input(cls, workdir, scf_input, manager=None, allocate=True):
 """ Create a `NonlinearFlow` for second order susceptibility calculations from an `AbinitInput` defining a ground-state run. Args: workdir: Working directory of the flow. scf_input: :class:`AbinitInput` object with the parameters for the GS-SCF run. manager: :class:`TaskManager` object. Read from `manager.yml` if None. allocate: True if the flow should be allocated before returning. Return: :class:`NonlinearFlow` object. """

        flow = cls(workdir, manager=manager)

        flow.register_scf_task(scf_input)
        scf_task = flow[0][0]

        nl_work = DteWork.from_scf_task(scf_task)

        flow.register_work(nl_work)

        if allocate: flow.allocate()

        return flow