human
I wrote the below code

    class ABCTest(fixtures.MappedTest, ):
        @classmethod
        def define_tables(cls, metadata):
            global ta, tb, tc
            ta = ['a', metadata]
            (ta.append(Column('id', Integer, primary_key=True, test_needs_autoincrement=True)),)
            ta.append(Column('a_data', String(30)))
            if (('a' == parent) and (direction == MANYTOONE)):
                ta.append(Column('child_id', Integer, ForeignKey(('%s.id' % child), use_alter=True, name='foo')))
            elif (('a' == child) and (direction == ONETOMANY)):
                ta.append(Column('parent_id', Integer, ForeignKey(('%s.id' % parent), use_alter=True, name='foo')))
            ta = Table(*ta)
            tb = ['b', metadata]
            tb.append(Column('id', Integer, ForeignKey('a.id'), primary_key=True))
            tb.append(Column('b_data', String(30)))
            if (('b' == parent) and (direction == MANYTOONE)):
                tb.append(Column('child_id', Integer, ForeignKey(('%s.id' % child), use_alter=True, name='foo')))
            elif (('b' == child) and (direction == ONETOMANY)):
                tb.append(Column('parent_id', Integer, ForeignKey(('%s.id' % parent), use_alter=True, name='foo')))
            tb = Table(*tb)
            tc = ['c', metadata]
            tc.append(Column('id', Integer, ForeignKey('b.id'), primary_key=True))
            tc.append(Column('c_data', String(30)))
            if (('c' == parent) and (direction == MANYTOONE)):
                tc.append(Column('child_id', Integer, ForeignKey(('%s.id' % child), use_alter=True, name='foo')))
            elif (('c' == child) and (direction == ONETOMANY)):
                tc.append(Column('parent_id', Integer, ForeignKey(('%s.id' % parent), use_alter=True, name='foo')))
            tc = Table(*tc)
        def teardown(self):
            if (direction == MANYTOONE):
                parent_table = {'a': ta, 'b': tb, 'c': tc}[parent]
                parent_table.update(values={parent_table.c.child_id: None}).execute()
           ...

What's a good function header?

=====
Here's a good function header?
assistant
#Here's a good function header.

def produce_test(parent, child, direction):