code: def slithir_cfg_to_dot(self, filename):
          
          from slither.core.cfg.node import NodeType
          with open(filename, 'w', encoding='utf8') as f:
              f.write('digraph{\n')
              for node in self.nodes:
                  label = 'Node Type: {} {}\n'.format(NodeType.str(node.type), node.node_id)
                  if node.expression:
                      label += '\nEXPRESSION:\n{}\n'.format(node.expression)
                  if node.irs:
                      label += '\nIRs:\n' + '\n'.join([str(ir) for ir in node.irs])
                  f.write('{}[label="{}"];\n'.format(node.node_id, label))
                  for son in node.sons:
                      f.write('{}->{};\n'.format(node.node_id, son.node_id))
  
              f.write("}\n")
docs: Export the function to a dot file
          Args:
              filename (str)