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.

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