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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 read_hector_output(csv_file):
 """ Reads a Hector output stream CSV file and returns a wide DataFrame with Hector output data. """

    # Filter out spin-up values. In Hector 1.x RCP output streams years are
    # given as end of simulation year.
    # See https://github.com/JGCRI/hector/issues/177
    start_year = 1746
    output_stream = pd.read_csv(csv_file, skiprows=1)

    wide = output_stream[output_stream.year >= start_year].pivot_table(
        index="year", columns="variable", values="value"
    )

    return wide