[Python] Using polymorphic_identity and inheritance is raising a warning

I have the following code, where I need to inherit GroupAB from GroupA because I want to use its functions vs copy-paste them again. since I can't use multiple values for polymorphic_identity=["GroupA", "GroupAB"] I tried using the below code yet it resulted with a warning

The main group is:

class Group(Base):
id = Column('id', Integer, primary_key=True)
name = Column('name', String(15))
g_type = Column('type', String(15))

__mapper_args__ = {
'polymorphic_on': g_type,
'polymorphic_identity': 'Group'
}


What I wished for:

class GroupCommon(Group):
__mapper_args__ = {
'polymorphic_identity': ['GroupA', 'GroupAB']
}

def some_function(self}:
....

# not possible, it doesn't accept a list - and raise:
if self.polymorphic_identity in self.polymorphic_map:
TypeError: unhashable type: 'list'


What I tried to do- is to inherit them:

class GroupA(Group):
__mapper_args__ = {
'polymorphic_identity': 'GroupA'
}

def some_function(self}:
....

class GroupAB(GroupA): <= Inherit from GroupA which is a polymorphic_identity of Group
__mapper_args__ = {
'polymorphic_identity': 'GroupAB'
}

pass # nothing here as i'm using GroupA's functions

# -- this works -- but raise a warning
SAWarning: Flushing object <GroupAB at 0x1082...> with incompatible polymorphic identity 'GroupAB'; the object may not refresh and/or load correctly
(this warning may be suppressed after 10 occurrences)


No warning when I use:

class GroupAB(Group): <= Inherit from Group, no functions available ofc
__mapper_args__ = {
'polymorphic_identity': 'GroupAB'
}

pass


Any thoughts ?

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