[yt-dev] Issue #837: Deposited Particle filter fields do not show up in derived_field_list (yt_analysis/yt)

[Nathan Goldbaum]

New issue 837: Deposited Particle filter fields do not show up in derived_field_list
https://bitbucket.org/yt_analysis/yt/issue/837/deposited-particle-filter-fields-do-not

Nathan Goldbaum:

Take the following example script:


```
#!python

import yt
import numpy as np
import pprint
from yt.data_objects.particle_filters import add_particle_filter
from matplotlib import pyplot as plt

def star(pfilter, data):
    filter = data["all", "particle_type"] == 2
    return filter

add_particle_filter("star", function=star, filtered_type="all",
                    requires=["particle_type"])

filename = "IsolatedGalaxy/galaxy0030/galaxy0030"

ds = yt.load(filename)
ds.add_particle_filter("star")

pprint.pprint(ds.derived_field_list)

```

While the particle fields for the "star" particle types do show up, only the deposit fields for `"io"` and `"all"` show up under the deposit ptype.  The deposit fields for the `"star"` ptype can be accessed through a data object, so the issue seems to be with the way deposit fields are added to the `derived_field_list` rather than the deposit fields themselves.