Unsupported type for problem: <class 'NoneType'>, when using ParticleSwarmAlgorithm

[zadnarock]

Hey Everyone, I am new to using this library and I am currently struck with the following error in my code.

class ContractCostTask(Task):
def init(self, graph, bdims, num_bonds):
print("Initializing ContractCostTask...")
super().init(dimension=num_bonds)
self.graph=graph
self.bdims=bdims
self.num_bonds=num_bonds

def _evaluate(self, x):
    print("HI")
    edge_ordering = np.argsort(x)+1
    result = logcontract(deepcopy(graph), bdims, edge_ordering)
    if result is None:
        result = np.inf
    return result

task = ContractCostTask(graph, bdims, num_bonds)
algorithm = ParticleSwarmAlgorithm(population_size=20, c1=1.5, c2=2.0, w=0.7, max_evals=num_greedy)
best_solution = algorithm.run(task)
print(best_solution).

TypeError Traceback (most recent call last)
in
18 print(bdims)
19 print(num_bonds)
---> 20 task = ContractCostTask(graph, bdims, num_bonds)
21 algorithm = ParticleSwarmAlgorithm(population_size=20, c1=1.5, c2=2.0, w=0.7, max_evals=num_greedy)
22 best_solution = algorithm.run(task)

1 frames
/usr/local/lib/python3.9/dist-packages/niapy/task.py in init(self, problem, dimension, lower, upper, optimization_type, repair_function, max_evals, max_iters, cutoff_value, enable_logging)
83 logger.warning('An instance of the Problem class was passed in, dimension, lower and upper parameters will be ignored.')
84 else:
---> 85 raise TypeError('Unsupported type for problem: {}'.format(type(problem)))
86
87 self.optimization_type = optimization_type

TypeError: Unsupported type for problem: <class 'NoneType'>. Initializing ContractCostTask... is printed but HI is not printed, which means the _evaluate function is not being called atleast once. Please help me find what I'm missing here.