Remove unused imports and use environment variables for storing API key

[gauthamk02]

1. The files in the repository contain many unused imports. Unused imports can cause performance issues, increased memory usage and security problems. Therefore it is important to keep remove them from the codebase. Some of the unused imports are:

app.py

import pandas as pd
import numpy as np

Experiments.ipynb

from sklearn.pipeline import make_pipeline
from sklearn.preprocessing import StandardScaler
from sklearn.linear_model import LogisticRegression
from sklearn.ensemble import GradientBoostingClassifier
from sklearn.tree import DecisionTreeClassifier
from sklearn.neural_network import MLPClassifier
from sklearn.svm import SVC
from sklearn.preprocessing import MinMaxScaler

2. Another problem is that the repository contains API key hardcoded in the file utils/weather_api.py. This is a high security concern as the API key is now public and anyone can use it. So the API key needs to be hidden away from the public using environment variables.