import yt

yt.enable_parallelism()

# Set the custom snapshot structure
my_field_def = ("Coordinates",
               "Velocities",
               "ParticleIDS",
               "Mass",
               ("Temperature", "Halo"),
               ("Density", "Halo"),
               ("SmoothingLength", "Halo"),)

# Load the snapshot
ds = yt.load('./snapshot_001-fake_gas-dspec-tspec', field_spec=my_field_def)

# Make the plot
prj = yt.ProjectionPlot(ds, fields=('deposit', 'Halo_density'), axis='z')
prj.save()