ENH: obtain also "nwb_version", ls it as NWB field in the table

I went for a shorter name in  ls  command since space is scarse.

Unfortunately I could not immediately figure out how to even populate
that field e.g. using NWBFile.  And PyNWB does not populate it
either ATM: NeurodataWithoutBorders/pynwb#1085

The only example I found quickly with nwb_version field populated was from
///crcns/ssc-7 dataset -- and in particular
data/L4E_whole_cell/Exp_2015-09-05_001_0001-0162.nwb
file there.

I really think we should come up with some good, and not that large collection
of sample .nwb files to test on.  Unfortunately any "real" .nwb file seems to be
quite large

dandi/cli/command.py

@@ -16,7 +16,10 @@
 
 from collections import OrderedDict
 
-from ..pynwb_utils import get_metadata
+from ..pynwb_utils import (
+    get_metadata,
+    get_nwb_version,
+)
 from ..support import pyout as pyouts
 
 lgr = get_logger()
@@ -66,8 +69,14 @@ def get_metadata_pyout(path):
             if v:
                 rec[f] = v
     except Exception as exc:
-        # lgr.error('Failed to get metadata from %s: %s', f, exc)
-        pass
+        lgr.debug('Failed to get metadata from %s: %s', path, exc)
+
+    if 'nwb_version' not in rec:
+        # Let's at least get that one
+        rec['NWB'] = get_nwb_version(path)
+    else:
+        # renames for more concise ls
+        rec['NWB'] = rec.pop('nwb_version', None)
     return rec
 
 
@@ -145,6 +154,7 @@ def ls(paths):
     out = pyout.Tabular(
         columns=[
             'path',
+            'NWB',
             'size',
             #'experiment_description',
             'lab',

dandi/pynwb_utils.py

@@ -1,6 +1,10 @@
 import h5py
 from pynwb import NWBHDF5IO
 
+from . import get_logger
+
+lgr = get_logger()
+
 # A list of metadata fields which dandi extracts from .nwb files.
 # Additional fields (such as `number_of_*`) might be added by the
 # get_metadata`
@@ -18,14 +22,39 @@
 )
 
 
+def get_nwb_version(filepath):
+    """Return a version of the NWB standard used by a file
+
+    Returns
+    -------
+    str or None
+       None if there is no version detected
+    """
+    with h5py.File(filepath, 'r') as h5file:
+        try:
+            return h5file['nwb_version'].value.decode
+        except KeyError:
+            lgr.debug('%s has no nwb_version' % filepath)
+
+
 def get_metadata(filepath):
     """Get selected metadata from a .nwb file
 
+    Parameters
+    ----------
+    filepath: str
+    query_nwb_version: bool, optional
+      Either to query/include nwb_version field
+
     Returns
     -------
     dict
     """
     out = dict()
+
+    # First read out possibly available versions of specifications for NWB(:N)
+    out['nwb_version'] = get_nwb_version(filepath)
+
     with NWBHDF5IO(filepath, 'r') as io:
         nwb = io.read()
         for key in metadata_fields: