code: def get_flattened_bsp_keys_from_schema(schema):
      
      keys = []
  
      for key in schema.declared_fields.keys():
          field = schema.declared_fields[key]
  
          if isinstance(field, mm.fields.Nested) and \
                  isinstance(field.schema, BoundSpatialPoint):
              keys.append("{}.{}".format(key, "position"))
  
      return keys
docs: Returns the flattened keys of BoundSpatialPoints in a schema
  
      :param schema: schema
      :return: list