minlen not present on TraitInstance

Loving traits! I have created a wrapper class that does some pretty printing among other things. I'm getting the following error when of my classes attributes is a List():

``` python

File "C:\Users\jeff\anaconda3\envs\dev\lib\site-packages\traits\trait_list_object.py", line 580, in __init__
self._validate_length(len(value))

File "C:\Users\jeff\anaconda3\envs\dev\lib\site-packages\traits\trait_list_object.py", line 889, in _validate_length
if not trait.minlen <= new_length <= trait.maxlen:

AttributeError: 'TraitInstance' object has no attribute 'minlen'
```

It's probably something I'm doing wrong, so let me know if you need more information from me. Thanks!