def load_problems(self):
"""Load the ProblemSets defined in the filename.
Yields:
The next ProblemSet defined in the file.
"""
with open(self.filename + '.txt', 'r') as fin:
lines = [a.strip() for a in fin.readlines()]
key = lines[0]
lines = lines[1:]
for line in lines:
problem_set = ProblemSet()
problem_set.init_line(line, key)
yield problem_set
