I have the following Table model representing a timeline.

class TimeRange(Base):

    __tablename__ = "time_line"

    record_id = Column(Integer, primary_key=True)
    level = Column(String, nullable=False) # e.g. "Point", "Range"
    content = Column(String, nullable=False)
    language_marker = Column(String) # this one column is optional and 
needs to be queried
    immediate_parent_id = Column(Integer, ForeignKey('time_line.record_id'))
    child_timelines = relationship('TimeRange', backref=backref(
'parent_timeline', remote_side=[record_id]))

The language_marker Column is the one that needs to be queried in a 
recursive manner. Not all records have such an attribute, and the business 
logic is: along the hierarchy lineage from the root down to the child 
timelines, at least one level of the TimeRange instance carries such an 
attribute, and the one in the lowest level should be returned. This works a 
little like cascading style sheet, where if the TimeRange object itself 
doesn't have such an attribute, just look further up one level above, util 
found one, and the latest defined style wins.

What is the technical direction I should look into to implement such 
queries? I'm using SQLAlchemy and the backend is SQLite. Thanks.

SQLAlchemy - 
The Python SQL Toolkit and Object Relational Mapper


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