GitLab

* add pairwise function for 'gaussian' and 'concatenation' mode

* rename test function

* decrease the complexity of nonlocal unittest

* fix typo and make unittest more complete

* add unittest when zero_init is False

* minor fix

* pack theta and phi
Co-authored-by: Jiarui XU <xvjiarui0826@gmail.com>

* add non_local module

* rewrite non local module comments

* perfect docstring and adjust init function

* not to init norm layer

* Correct initialize when there is a norm

* set normal method for both embedded_gaussian and dot_product