class_docstr: This class represents a directed graph using adjacency lists
class_docstr_tok: ["This","class","represents","a","directed","graph","using","adjacency","lists"]
code: def __init__(self, vertices):
      # No. of vertices
      self.vertex_count = vertices
  
      # default dictionary to store graph
      self.graph = {}
  
      # To store transitive closure
      self.closure = [
          [0 for j in range(vertices)] for i in range(vertices)
      ]
  
label_desc: Use image node_id 1 to create a new Graph object  with example: obj = Graph(vertices)