python pubtator fix

[xusliebana]

The Pubtutor class doesn't work in python

Description

We need to use a case class instead of an object.The Pubtotor python class cannot load the object from scala.
We also add a parameter to allow work with Pubtator files that don't have codes with paddings.

Motivation and Context

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Code improvements with no or little impact
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING page.
• I have added tests to cover my changes.
• All new and existing tests passed.