$($a$)$ Write code that uses scikit$-$learn to train a linear regression model

using the California housing dataset.

$($b$)$ Write code that uses scikit$-$learn to train a logistic regression model

for binary classification using the breast cancer dataset.

$($c$)$ Write code that uses scikit$-$learn to train a logistic regression model

for multiclass classification using the iris dataset.

In each case, split the dataset into training and validation datasets. Use

the training dataset to train your model, then use the validation dataset

to evaluate the accuracy of your model.