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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 map_columns(col):
 """Map data element numbers to pvlib names. Parameters col: str Column label to be mapped. Returns ------- str The pvlib label if it was found in the mapping, else the original label. """

    if col.startswith('7'):
        # spectral data
        try:
            return VARIABLE_MAP[col]
        except KeyError:
            return col
    try:
        variable_name = VARIABLE_MAP[col[:3]]
        variable_number = col[3:]
        return variable_name + '_' + variable_number
    except KeyError:
        return col