Long waiting time when executing cache.get_session_table() function

[NeoNeuron]

Describe the bug
When executing cache.get_session_table() function, the download of corresponding *.csv file completed immediately. However, the get_session_table function would just hang there for minutes before it returned the DataFrame.

To Reproduce
https://allensdk.readthedocs.io/en/latest/_static/examples/nb/ecephys_data_access.html

import os
import shutil

import numpy as np
import pandas as pd

from allensdk.brain_observatory.ecephys.ecephys_project_cache import EcephysProjectCache
data_directory = '/local1/ecephys_cache_dir' # must be updated to a valid directory in your filesystem

manifest_path = os.path.join(data_directory, "manifest.json")
cache = EcephysProjectCache.from_warehouse(manifest=manifest_path)

sessions = cache.get_session_table()
probes = cache.get_probes()
channels = cache.get_channels()
units = cache.get_units()

Expected behavior
Return DataFrames of sessions, probes, channels, and units shortly after the cache download these four files:

1. sessions.csv (7.8 kB)
2. probes.csv (27.0 kB)
3. channels.csv (6.6 MB)
4. units.csv (51.4 MB)

Actual Behavior
The download of these four *.csv files completed immediately. However, the "get" function would just hang there for minutes before it returned the DataFrame.

Environment (please complete the following information):

• OS & version: macOS 10.15.3
• Python version: 3.7.8
• AllenSDK version: 2.1.0

Additional context
To bypass this slow data fetch issue with cache, I manually downloaded *.nwb files from DANDI Archive, and use EcephysSession.from_nwb_path() function to import raw *.nwb files. However, it seems that I cannot manually import LFP data of specific probes from local *.nwb files.

Is there any api or function that can provide way to do this?

Many thanks!

[NeoNeuron]

Also, I tested cache module in under Python version.

Environment

• OS: macOS 10.15.3
• Python version: 3.7.4
• AllenSDK version: 2.1.0
• pynwb version: 1.3.2
• hdmf version: 1.6.3

It looks around 13 mins to complete this line below.

sessions = cache.get_session_table()

And it downloaded all four *.csv files in my working directory. And after that, the rest three get functions completed around 1 second for each.

probes = cache.get_probes()
channels = cache.get_channels()
units = cache.get_units()

In short, as long as all four *.csv files existing in the data_directory, the get functions of cache module work well. Otherwise, it took way more time.

I think it might lead from the slow download speed for these *.csv files. Maybe it would be much easier if the download links of these csv files can be provided for manual download.