dexy datas -alias keyvalue
was my best guess of what to do from this

root@a7c70420830a:~/notebooks/CogU# dexy datas

bs4
etree
generic
keyvalue
sectioned

For more information about a particular data type,
use the -alias flag and specify the data type alias.

root@a7c70420830a:~/notebooks/CogU# dexy datas -alias keyvalue

keyvalue

Data class for key-value data.

Methods:
append
Traceback (most recent call last):
File "/opt/conda/envs/python2/bin/dexy", line 9, in
load_entry_point('dexy==1.0.14', 'console_scripts', 'dexy')()
File "/opt/conda/envs/python2/lib/python2.7/site-packages/dexy/commands/init.py", line 53, in run
parse_and_run_cmd(resolve_argv())
File "/opt/conda/envs/python2/lib/python2.7/site-packages/dexy/commands/init.py", line 111, in parse_and_run_cmd
args.parse_and_run_command(argv, module, default_command)
File "/opt/conda/envs/python2/lib/python2.7/site-packages/modargs/args.py", line 381, in parse_and_run_command
command_module(mod, command, options, cli_options=cli_options)
File "/opt/conda/envs/python2/lib/python2.7/site-packages/modargs/args.py", line 286, in command_module
function(*options)
File "/opt/conda/envs/python2/lib/python2.7/site-packages/dexy/commands/env.py", line 96, in datas_command
raise dexy.exceptions.InternalDexyProblem("Must provide docstring for %s" % k)
dexy.exceptions.InternalDexyProblem: Oops! You may have found a bug in Dexy. The developer would really appreciate if you copy and paste this entire message and the Traceback above it into an email and send to info@dexy.it Your version of Dexy is 1.0.14 Your platform is Linux
Must provide docstring for append