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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 process_tree(top, name='top'):
 """Creates a string representation of the process tree for process top. This method uses the :func:`walk_processes` method to create the process tree. :param top: top process for which process tree string should be created :type top: :class:`~climlab.process.process.Process` :param str name: name of top process :returns: string representation of the process tree :rtype: str :Example: :: model: <class 'climlab.model.ebm.EBM'> diffusion: <class 'climlab.dynamics.diffusion.MeridionalDiffusion'> LW: <class 'climlab.radiation.AplusBT.AplusBT'> albedo: <class 'climlab.surface.albedo.StepFunctionAlbedo'> iceline: <class 'climlab.surface.albedo.Iceline'> cold_albedo: <class 'climlab.surface.albedo.ConstantAlbedo'> warm_albedo: <class 'climlab.surface.albedo.P2Albedo'> insolation: <class 'climlab.radiation.insolation.P2Insolation'> """

    str1 = ''
    for name, proc, level in walk_processes(top, name, ignoreFlag=True):
        indent = ' ' * 3 * (level)
        str1 += ('{}{}: {}\n'.format(indent, name, type(proc)))
    return str1