def add_edge(self, u, v): if 0 <= u < self.size and 0 <= v < self.size: self.adj_matrix[u][v] = 1 self.adj_matrix[v][u] = 1

This is a Python function named add_edge that belongs to a class (probably a Graph class). This function is used to add an edge between two nodes in a graph. Here's a step-by-step explanation:

1. The function add_edge takes three parameters: self, u, and v. self is a default parameter in Python class methods and refers to the instance of the class, u and v are probably the nodes between which an edge is to be added.

2. The if statement checks whether u and v are within the valid range. The valid range is between 0 and the size of the graph (exclusive). If u or v is not within this range, the function will not proceed to add an edge.

3. If u and v are within the valid range, the function proceeds to add an edge between these nodes. In the adjacency matrix representation of a graph, an edge between nodes u and v is represented by setting self.adj_matrix[u][v] and self.adj_matrix[v][u] to 1. This is because the graph is undirected, so an edge from u to v is the same as an edge from v to u.

4. The function does not return any value. It modifies the adjacency matrix of the graph in-place.