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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 list_formats(format_type, backend=None):
 """ Returns list of supported formats for a particular backend. """

    if backend is None:
        backend = Store.current_backend
        mode = Store.renderers[backend].mode if backend in Store.renderers else None
    else:
        split = backend.split(':')
        backend, mode = split if len(split)==2 else (split[0], 'default')

    if backend in Store.renderers:
        return Store.renderers[backend].mode_formats[format_type][mode]
    else:
        return []