def load(self, requirements_file=None):
        """Load or reload requirements from a requirements.txt file.

        :param requirements_file: if not given, the filename used from
            initialization will be read again.
        """
        if requirements_file is None:
            requirements_file = self.filename
            if requirements_file is None:
                raise ValueError("no filename provided")
        elif isinstance(requirements_file, text_type):
            requirements_file = Path(requirements_file)
        self.clear()
        with requirements_file.open() as f:
            self.loads(f.read())

        if isinstance(requirements_file, (text_type, Path)):
            self.filename = requirements_file
def set_deadline(cls, course_key, deadline, is_explicit=False):
        """
        Configure the verification deadline for a course.

        If `deadline` is `None`, then the course will have no verification
        deadline.  In this case, users will be able to verify for the course
        at any time.

        Arguments:
            course_key (CourseKey): Identifier for the course.
            deadline (datetime or None): The verification deadline.

        """
        if deadline is None:
            VerificationDeadline.objects.filter(course_key=course_key).delete()
        else:
            record, created = VerificationDeadline.objects.get_or_create(
                course_key=course_key,
                defaults={"deadline": deadline, "deadline_is_explicit": is_explicit}
            )

            if not created:
                record.deadline = deadline
                record.deadline_is_explicit = is_explicit
                record.save()