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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 list_of_vars(arg_plot):
 """Construct list of variables per plot. Args: arg_plot (str):
 string with variable names separated with ``_`` (figures), ``.`` (subplots) and ``,`` (same subplot). Returns: three nested lists of str - variables on the same subplot; - subplots on the same figure; - figures. """

    lovs = [[[var for var in svars.split(',') if var]
             for svars in pvars.split('.') if svars]
            for pvars in arg_plot.split('-') if pvars]
    lovs = [[slov for slov in lov if slov] for lov in lovs if lov]
    return [lov for lov in lovs if lov]