Fix filter job

[yanchengnv]

Fixes # .

Description

Currently when adding multiple filters, Job API would fail. This PR fixes the issue.

A filter can be added to a set of tasks (e.g. ["train", "validate"]). All task sets must be unique, meaning that task sets must not have intersections.

For example, if you add a filter X to task set ["train", "validate"], you cannot add another filter Y to task set ["train", "eval"], because these two task share the same element "train". Of course, if you make each task set to contain a single task, then it's okay to add any filters.

You can add any number of filters to the same task set.

Types of changes

• Non-breaking change (fix or new feature that would not break existing functionality).
• Breaking change (fix or new feature that would cause existing functionality to change).
• New tests added to cover the changes.
• Quick tests passed locally by running ./runtest.sh.
• In-line docstrings updated.
• Documentation updated.

[chesterxgchen]

LGTM

[chesterxgchen]

/build

[YuanTingHsieh]

Logic LGTM,

We need to add in our doc the assumption of
"A filter can be added to a set of tasks (e.g. ["train", "validate"]). All task sets must be unique, meaning that task sets must not have intersections."