pip install pydot==1.2.3

Here is what the above code is Doing:
1. Importing the required libraries
2. Loading the dataset
3. Splitting the dataset into training and testing sets
4. Creating the decision tree classifier
5. Fitting the classifier to the training set
6. Predicting the class labels of the test set
7. Creating the confusion matrix
8. Visualizing the training set results
9. Visualizing the test set results