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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 _import_matplotlib():
 """Import matplotlib safely."""

    # make sure that the Agg backend is set before importing any
    # matplotlib
    import matplotlib
    matplotlib.use('agg')
    matplotlib_backend = matplotlib.get_backend().lower()

    if matplotlib_backend != 'agg':
        raise ValueError(
            "Sphinx-Gallery relies on the matplotlib 'agg' backend to "
            "render figures and write them to files. You are "
            "currently using the {} backend. Sphinx-Gallery will "
            "terminate the build now, because changing backends is "
            "not well supported by matplotlib. We advise you to move "
            "sphinx_gallery imports before any matplotlib-dependent "
            "import. Moving sphinx_gallery imports at the top of "
            "your conf.py file should fix this issue"
            .format(matplotlib_backend))

    import matplotlib.pyplot as plt
    return matplotlib, plt