import yt
import numpy as np
from yt.data_objects.particle_filters import add_particle_filter
from matplotlib import pyplot as plt
def formed_star(pfilter, data):
    filter = data["io", "creation_time"] > 0
    return filter
add_particle_filter("formed_star", function=formed_star, filtered_type='io',
                    requires=["creation_time"])
filename = "/Users/xxxxxx/Desktop/out/info_00014.txt"
ds = yt.load(filename)
ds.add_particle_filter('formed_star')
ad = ds.all_data()
masses = ad['formed_star', 'particle_mass'].in_units('Msun')
formation_time = ad['formed_star', 'creation_time'].in_units('yr')
time_range = [0, 5e9] # years
n_bins = 1000
hist, bins = np.histogram(formation_time, bins=n_bins, range=time_range,)
inds = np.digitize(formation_time, bins=bins)

time = (bins[:-1] + bins[1:])/2
sfr = np.array([masses[inds == j+1].sum()/(bins[j+1]-bins[j])
                for j in range(len(time))])
sfr[sfr == 0] = np.nan
plt.plot(time/1e6, sfr)
plt.xlabel('Time  [Myr]')

The fields

('io', 'creation_time'),

required by the "formed_star" particle filter, are not defined for this dataset.