Obtaining the retention time and ActivationType (e.g., HCD) from mgf files using Depthcharge about depthcharge HOT 1 CLOSED

mgf_contents = """\
BEGIN IONS
PEPMASS=1000.0
CHARGE=3+
NCE=25.0
FOO=BAR
10.0 1234.5
20.0 6789.0
END IONS
"""

with open("example.mgf", "w+") as mgf_out:
    mgf_out.write(mgf_contents)

from pyteomics.mgf import MGF

with MGF("example.mgf") as mgf_in:
    print(next(mgf_in))

# {   'charge array': masked_array(data=[--, --],
#             mask=[ True,  True],
#       fill_value=0,
#            dtype=int64),
#    'intensity array': array([1234.5, 6789. ]),
#    'm/z array': array([10., 20.]),
#    'params': {   'charge': [3],
#                  'foo': 'BAR',
#                  'nce': '25.0',
#                  'pepmass': (1000.0, None)}}

import pyarrow as pa
import depthcharge as dc
from depthcharge.data import CustomField

df = dc.data.spectra_to_df(
    "example.mgf", 
    custom_fields=[
        CustomField("NCE", lambda s: s["params"]["nce"], pa.string()),
        CustomField("foo", lambda s: s["params"]["foo"], pa.string())
    ],
)

print(df)

#┌─────────────┬─────────┬──────────┬──────────────┬───┬───────────┬─────────────────┬──────┬─────┐
#│ peak_file   ┆ scan_id ┆ ms_level ┆ precursor_mz ┆ … ┆ mz_array  ┆ intensity_array ┆ NCE  ┆ foo │
#│ ---         ┆ ---     ┆ ---      ┆ ---          ┆   ┆ ---       ┆ ---             ┆ ---  ┆ --- │
#│ str         ┆ str     ┆ u8       ┆ f64          ┆   ┆ list[f64] ┆ list[f64]       ┆ str  ┆ str │
#╞═════════════╪═════════╪══════════╪══════════════╪═══╪═══════════╪═════════════════╪══════╪═════╡
#│ example.mgf ┆ 0       ┆ 2        ┆ 1000.0       ┆ … ┆ [20.0]    ┆ [1.0]           ┆ 25.0 ┆ BAR │
#└─────────────┴─────────┴──────────┴──────────────┴───┴───────────┴─────────────────┴──────┴─────┘