Autogenerate cannot detect partial indexes (with postgresql_where) on postgres

alembic==1.4.3
SQLAlchemy==1.3.20

I have a feeling that I had alembic autogenerate working for following models:

class UTCNow(expression.FunctionElement):
    type = DateTime()


@compiles(UTCNow, 'postgresql')
def pg_utcnow(element, compiler, **kw):
    return "TIMEZONE('utc', CURRENT_TIMESTAMP)"


@compiles(CreateColumn, 'postgresql')
def use_identity(element, compiler, **kw):
    return compiler.visit_create_column(element, **kw).replace('SERIAL', 'INT GENERATED BY DEFAULT AS IDENTITY')


class CharacterStatus(enum.IntEnum):
    DEAD = 0
    ALIVE = 1


class BaseDBModel:
    id = Column(Integer, primary_key=True)
    created_at = Column(DateTime, server_default=UTCNow())
    updated_at = Column(DateTime, onupdate=UTCNow())


class Characters(BaseDBModel, Base):
    __tablename__ = 'characters'

    deleted_at = Column(DateTime)

    name = Column(String)
    birthday = Column(Date)
    img = Column(String, nullable=True)
    status = Column(Enum(CharacterStatus), default=CharacterStatus.ALIVE)
    nickname = Column(String)
    occupation = Column(ARRAY(String))
    appearance = Column(ARRAY(String))
    portrayed = Column(String)
    category = Column(ARRAY(String))

    __table_args__ = (
        Index('uq_characters_name', text('lower(name)'), unique=True, postgresql_where=(deleted_at.is_(None))),
        Index('uq_characters_nickname', text('lower(nickname)'), unique=True, postgresql_where=(deleted_at.is_(None))),
    )

but for some reason I don't get Indexes in migration file:
alembic revision --autogenerate -m "initial"

"""initial

Revision ID: f4eb64f96910
Revises: 
Create Date: 2020-10-27 22:01:11.634916+00:00

"""
from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = 'f4eb64f96910'
down_revision = None
branch_labels = None
depends_on = None


def upgrade():
    schema_upgrades()
    data_upgrades()


def downgrade():
    data_downgrades()
    schema_downgrades()


def schema_upgrades():
    """schema upgrade migrations go here."""
    # ### commands auto generated by Alembic - please adjust! ###
    op.create_table('characters',
    sa.Column('id', sa.Integer(), nullable=False),
    sa.Column('created_at', sa.DateTime(), server_default=sa.text("TIMEZONE('utc', CURRENT_TIMESTAMP)"), nullable=True),
    sa.Column('updated_at', sa.DateTime(), nullable=True),
    sa.Column('deleted_at', sa.DateTime(), nullable=True),
    sa.Column('name', sa.String(), nullable=True),
    sa.Column('birthday', sa.Date(), nullable=True),
    sa.Column('img', sa.String(), nullable=True),
    sa.Column('status', sa.Enum('DEAD', 'ALIVE', name='characterstatus'), nullable=True),
    sa.Column('nickname', sa.String(), nullable=True),
    sa.Column('occupation', sa.ARRAY(sa.String()), nullable=True),
    sa.Column('appearance', sa.ARRAY(sa.String()), nullable=True),
    sa.Column('portrayed', sa.String(), nullable=True),
    sa.Column('category', sa.ARRAY(sa.String()), nullable=True),
    sa.PrimaryKeyConstraint('id')
    )
    op.create_table('locations',
    sa.Column('id', sa.Integer(), nullable=False),
    sa.Column('created_at', sa.DateTime(), server_default=sa.text("TIMEZONE('utc', CURRENT_TIMESTAMP)"), nullable=True),
    sa.Column('updated_at', sa.DateTime(), nullable=True),
    sa.Column('character_id', sa.Integer(), nullable=False),
    sa.Column('timestamp', sa.DateTime(), nullable=True),
    sa.Column('coordinates', geoalchemy2.types.Geography(geometry_type='POINT', srid=4326, from_text='ST_GeogFromText', name='geography'), nullable=True),
    sa.ForeignKeyConstraint(['character_id'], ['characters.id'], ),
    sa.PrimaryKeyConstraint('id')
    )
    # ### end Alembic commands ###


def schema_downgrades():
    """schema downgrade migrations go here."""
    # ### commands auto generated by Alembic - please adjust! ###
    op.drop_table('locations')
    op.drop_table('characters')
    # ### end Alembic commands ###


def data_upgrades():
    """Add any optional data upgrade migrations here!"""
    pass


def data_downgrades():
    """Add any optional data downgrade migrations here!"""
    pass

Is there a way to pick them automagically? Thanks

Start by reproducing the supplied models with alembic revision --autogenerate -m "initial" and inspect the generated migration file. Trace autogenerate's PostgreSQL index comparison and reflection path; done means the partial indexes using postgresql_where appear correctly in the migration.