Serialize geometry using flask-marshmallow

I know this is pretty old, but answering now as I just solved this for myself after landing on this question. The way I accomplished it is just by adding a method field to my schema like so:

from marshmallow_sqlalchemy import SQLAlchemySchema, fieldsfrom geoalchemy2.shape import to_shapefrom common.models import Nodeclass NodeSchema(SQLAlchemySchema):    class Meta:        model = Node    geom = fields.fields.Method("geomToPoint")    def geomToPoint(self, obj):        return to_shape(obj.geom)

This returns the Geometry field as a Shapely shape field, something like POINT (39.2934324 -123.59348) which is what I was looking for.

marshmallow_sqlalchemy do not know how to serialize the field geom of type Geometry. This is because GeoAlchemy is not directly supported in marshmallow. In order to solve this you need to write a custom ModelConverter which tells marshmallow how to serialize a field of type Geometry.

from geoalchemy2.types import Geometry as GeometryTypefrom marshmallow_sqlchemy.convert import ModelConverter as BaseModelConverterclass ModelConverter(BaseModelConverter):    SQLA_TYPE_MAPPING = {        **BaseModelConverter.SQLA_TYPE_MAPPING,        **{GeometryType: fields.Field()},    }class EstateSchema(ma.ModelSchema):    class Meta:        model = Estates        model_converter = ModelConverter

The same has been mentioned in the github repository of marshmallow-sqlalchemy