Check the data_type of returned chunk of plugin

[dachengx]

What is the problem / what does the code in this PR do

This is a simple check to make sure that the data_type of the returned chunk is as promised.

Can you briefly describe how it works?

Can you give a minimal working example (or illustrate with a figure)?

Please include the following if applicable:

• Update the docstring(s)
• Update the documentation
• Tests to check the (new) code is working as desired.
• Does it solve one of the open issues on github?

Please make sure that all automated tests have passed before asking for a review (you can save the PR as a draft otherwise).

[coveralls]

coverage: 89.063% (+0.001%) from 89.062%
when pulling 1262614 on check_chunk_data_type
into 6284908 on master.