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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 perform_exe_expansion(self):
 """ This function will look through the executables section of the ConfigParser object and replace any values using macros with full paths. For any values that look like ${which:lalapps_tmpltbank} will be replaced with the equivalent of which(lalapps_tmpltbank) Otherwise values will be unchanged. """

        # Only works on executables section
        if self.has_section('executables'):
            for option, value in self.items('executables'):
                # Check the value
                newStr = self.interpolate_exe(value)
                if newStr != value:
                    self.set('executables', option, newStr)