* add initializers and BaseModule for unified parameter initialization
* fix circle import
* bug fix
* add is_init flag in BaseModule
* fix docstring
* sort import and fix doc format
* fix bug
* fix docformat and double quote string
* fix import sort
* import sort
* sort import
* revise according to comments
* fix doc format
* revise according to comments
* revise import and fix typo
* polish code
* revise minors
* revice minors
* revise apply function
* revise bias initialization with probability
* add type test for bias_prob
* revise minors