Parse entities from an entity section (People, Organizations, Events).
The body is the text between the H2 heading and the next H2 heading.
section_start_line is the line number of the H2 heading in the original file.
Parse a single entity from a standalone entity file body.
The body is the text after the H1 heading (bullet fields, no H3 headings).
label is determined by the file’s directory (people/ or organizations/).
id comes from the front matter (may be None).