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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 _get_backend(name: str = None):
 """Get a plotting backend. Tries to get it using the name - or the default one. """

    if not backends:
        raise RuntimeError("No plotting backend available. Please, install matplotlib (preferred) or bokeh (limited).")
    if not name:
        name = _default_backend
    if name == "bokeh":
        raise RuntimeError("Support for bokeh has been discontinued. At some point, we may return to support holoviews.")
    backend = backends.get(name)
    if not backend:
        raise RuntimeError("Backend {0} does not exist. Use one of the following: {1}".format(name, ", ".join(backends.keys())))
    return name, backends[name]