Debug a training loop where epochs 2 and 3 do nothing

import json

def load_examples(path):
    with open(path) as f:
        for line in f:
            yield json.loads(line)

examples = load_examples("train.jsonl")
print("examples:", len(examples))

for epoch in range(3):
    total = 0
    for ex  examples:
        total += train_step(ex)
    (epoch, total)