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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 bus_line_names(self):
 """Append bus injection and line flow names to `varname`"""

        if self.system.tds.config.compute_flows:
            self.system.Bus._varname_inj()
            self.system.Line._varname_flow()
            self.system.Area._varname_inter()