<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def delta_nu(self, *args):
 """Returns asteroseismic delta_nu in uHz reference: https://arxiv.org/pdf/1312.3853v1.pdf, Eq (2) """

        return 134.88 * np.sqrt(self.mass(*args) / self.radius(*args)**3)