Increase Pylint Score for the current codebase

# Improve Pylint Coverage and Code Quality in EvalAI

## Description
We recently added pylint to our CI pipeline with a minimum score requirement of 5.0, but we need to improve our overall pylint score and fix common code quality issues throughout the codebase.

## Current Status
- Pylint has been integrated into our Travis CI pipeline
- Current pylint score is below the acceptable threshold :(
- Refer here: https://app.travis-ci.com/github/Cloud-CV/EvalAI/jobs/631902183
- Multiple error categories are being reported that need fixing

## Objectives
1. Identify and fix common pylint errors and warnings
2. Increase the overall pylint score from current level to at least 7.5
3. Standardize code quality across the codebase

## Proposed Tasks
- [ ] Address unused imports and variables (typically detected by C0410, W0611)
- [ ] Fix line length issues to comply with PEP 8 (79 characters)
- [ ] Add missing docstrings to modules, classes, and functions
- [ ] Fix poor variable naming and code style issues

1. First fix all error-level issues (--errors-only)
2. Then address warning-level issues
3. Finally work on convention and refactor messages