section_title
section_title(
line: Text ,
depth: int ,
)-> ‘Text’
How a terminal draws the line which names a block.
A block below the top starts on a line of its own, set in by how deep it sits; the top of a tree opens wherever its container left off, so it is drawn as it stands. Every line is set in, not just the first: a field value may hold a newline – a description usually does – and a continuation left at column zero reads as a block of its own.