How to use the rebound.units.hash_to_unit function in rebound

Mearth      : Earth masses
        Mmars       : Mars masses
        Mjupiter    : Jupiter masses
        Msaturn     : Saturn masses
        Muranus     : Neptune masses
        Mpluto      : Pluto masses
        
        Examples
        --------
        
        >>> sim = rebound.Simulation()
        >>> sim.units = ('yr', 'AU', 'Msun')

        """
        
        return {'length':hash_to_unit(self.python_unit_l), 'mass':hash_to_unit(self.python_unit_m), 'time':hash_to_unit(self.python_unit_t)}

def convert_particle_units(self, *args): 
        """
        Will convert the units for the simulation (i.e. convert G) as well as the particles' cartesian elements.
        Must have set sim.units ahead of calling this function so REBOUND knows what units to convert from.

        Parameters
        ----------
        3 strings corresponding to units of time, length and mass.  Can be in any order and aren't case sensitive.        You can add new units to rebound/rebound/units.py
        """
        if self.python_unit_l == 0 or self.python_unit_m == 0 or self.python_unit_t == 0:
            raise AttributeError("Must set sim.units before calling convert_particle_units in order to know what units to convert from.")
        new_l, new_t, new_m = check_units(args)
        for p in self.particles:
            units_convert_particle(p, hash_to_unit(self.python_unit_l), hash_to_unit(self.python_unit_t), hash_to_unit(self.python_unit_m), new_l, new_t, new_m)
        self.update_units((new_l, new_t, new_m))

5) A list of particles or names.
        """
        if particle is not None:
            if isinstance(particle, Particle):
                if (self.gravity == "tree" or self.collision == "tree") and self.root_size <=0.:
                    raise ValueError("The tree code for gravity and/or collision detection has been selected. However, the simulation box has not been configured yet. You cannot add particles until the the simulation box has a finite size.")

                clibrebound.reb_add(byref(self), particle)
            elif isinstance(particle, list):
                for p in particle:
                    self.add(p, **kwargs)
            elif isinstance(particle,str):
                if self.python_unit_l == 0 or self.python_unit_m == 0 or self.python_unit_t == 0:
                    self.units = ('AU', 'yr2pi', 'Msun')
                self.add(horizons.getParticle(particle, **kwargs), hash=particle)
                units_convert_particle(self.particles[-1], 'km', 's', 'kg', hash_to_unit(self.python_unit_l), hash_to_unit(self.python_unit_t), hash_to_unit(self.python_unit_m))
            else: 
                raise ValueError("Argument passed to add() not supported.")
        else: 
            self.add(Particle(simulation=self, **kwargs))
        if hasattr(self, '_widgets'):
            self._display_heartbeat(pointer(self))