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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def populate_database():
 """Populate the database with some data useful for development."""

    if User.fetch_by(username='admin'):
        return

    # Admin user
    admin = User(name='Administrator', password='password',
                 username='admin', is_admin=True)
    # Class
    class_ = Class(name='CS32')
    Session.add(class_)
    Session.flush()

    # Project
    project = Project(name='Project 1', class_id=class_.id)
    Session.add(project)
    Session.flush()

    # File verification
    fv = FileVerifier(filename='test.c', min_size=3, min_lines=1,
                      project_id=project.id)

    Session.add_all([admin, fv])
    try:
        transaction.commit()
        print('Admin user created')
    except IntegrityError:
        transaction.abort()