class B(Document):
a = StringField(format="something wrong")
class C(Document):
a = StringField(min_length='a')
class D(Document):
a = StringField(max_length='a')
class A(Document):
a = StringField(pattern=1)
class A(Document):
a = StringField(pattern=".", default="a", min_length=1, max_length=1)
class A(Document):
a = CompoundField(one_of=[StringField(), IntField()])
class A(Document):
a = StringField()
class B(A):
b = StringField()
class B(Document):
b = StringField()