The hammer command should elaborate on the issue with the types if the argument is required "--content-type".

For Example:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Invalid content-type. Valid content-types are: a, b, c, or d
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Also, we tried adding the flag --content-type with ansible_collection,docker,file,yum.

1. hammer content-units list --content-type yum

--|----|-------|--------
ID | NAME | VERSION | FILENAME
--|----|-------|--------

1. hammer content-units list --content-type --help
   --|----|-------|--------
   ID | NAME | VERSION | FILENAME
   --|----|-------|--------
    
2. hammer content-units list --content-type
   Missing arguments for '--content-type'.
    
3. hammer content-units list
   Missing arguments for '--content-type'.
    
4. hammer content-units list --content-type
   Missing arguments for '--content-type'.
    
5. hammer content-units list --content-view-id 2
   Missing arguments for '--content-type'.
    
6. hammer content-units list --content-view-id 2 --content-type
   Missing arguments for '--content-type'.