Unable to read in "time_slide" ligolw table through `EventTable.read()`

Created by: myNameIsPatrick

This should hopefully give a minimal example with a ligolw-formatted file with a time slide table contained within.

>>> EventTable.read("path/to/ligolw_file.xml.gz", tablename="time_slide")

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/table/table.py", line 241, in read
    return io_read_multi(vstack, cls, source, *args, **kwargs)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/io/mp.py", line 92, in read_multi
    output = mp_utils.multiprocess_with_queues(
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/utils/mp.py", line 123, in multiprocess_with_queues
    return list(map(_inner, inputs))
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/utils/mp.py", line 118, in _inner
    return func(x)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/io/mp.py", line 121, in _read_single_file
    return fobj, io_read(cls, fobj, *args, **kwargs)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/astropy/io/registry.py", line 523, in read
    data = reader(*args, **kwargs)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/table/io/utils.py", line 67, in wrapper
    tab = func(*args, **kwargs)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/table/io/ligolw.py", line 395, in read_table
    return Table(read_ligolw_table(source, tablename=tablename, **read_kw),
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/astropy/table/table.py", line 436, in __init__
    data = data.__astropy_table__(self.__class__, copy, **kwargs)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/table/io/ligolw.py", line 160, in to_astropy_table
    arr = _get_column(llwtable, colname)
  File "/home/patrick.godwin/.conda/envs/idq-dev/lib/python3.8/site-packages/gwpy/table/io/ligolw.py", line 186, in _get_column
    return getattr(llwtable, get_)()
TypeError: get_time_slide_id() missing 1 required positional argument: 'offsetdict'

I'm not sure why it's trying to call get_time_slide_id() as it appears to be an extra method that's only defined for the time slide table.