docs: def set_edist_powerlaw(self, emin_mev, emax_mev, delta, ne_cc):
          """Set the energy distribution function to a power law.
  
          **Call signature**
  
          *emin_mev*
            The minimum energy of the distribution, in MeV
          *emax_mev*
            The maximum energy of the distribution, in MeV
          *delta*
            The power-law index of the distribution
          *ne_cc*
            The number density of energetic electrons, in cm^-3.
          Returns
            *self* for convenience in chaining.
          """
          if not (emin_mev >= 0):
              raise ValueError('must have emin_mev >= 0; got %r' % (emin_mev,))
          if not (emax_mev >= emin_mev):
              raise ValueError('must have emax_mev >= emin_mev; got %r, %r' % (emax_mev, emin_mev))
          if not (delta >= 0):
              raise ValueError('must have delta >= 0; got %r, %r' % (delta,))
          if not (ne_cc >= 0):
              raise ValueError('must have ne_cc >= 0; got %r, %r' % (ne_cc,))
  
          self.in_vals[IN_VAL_EDIST] = EDIST_PLW
          self.in_vals[IN_VAL_EMIN] = emin_mev
          self.in_vals[IN_VAL_EMAX] = emax_mev
          self.in_vals[IN_VAL_DELTA1] = delta
          self.in_vals[IN_VAL_NB] = ne_cc
          return self