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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 mono_resolution( grooves_per_mm, slit_width, focal_length, output_color, output_units="wn" ) -> float: """Calculate the resolution of a monochromator. Parameters grooves_per_mm : number Grooves per millimeter. slit_width : number Slit width in microns. focal_length : number Focal length in mm. output_color : number Output color in nm. output_units : string (optional) Output units. Default is wn. Returns ------- float Resolution. """

    d_lambda = 1e6 * slit_width / (grooves_per_mm * focal_length)  # nm
    upper = output_color + d_lambda / 2  # nm
    lower = output_color - d_lambda / 2  # nm
    return abs(
        wt_units.converter(upper, "nm", output_units)
        - wt_units.converter(lower, "nm", output_units)
    )