proc loadYaml(fileName: string): Graph {...}{.raises: [IOError, OSError,
    YamlParserError, YamlConstructionError, Exception, KeyError, ValueError],
    tags: [ReadIOEffect, RootEffect, WriteIOEffect, TimeEffect].}

proc saveYaml(g: Graph; fileName: string; force_overwrite: bool = false) {...}{.raises: [
    IOError, ValueError, KeyError, YamlPresenterJsonError,
    YamlPresenterOutputError, YamlStreamError, Exception, OSError],
    tags: [ReadDirEffect, RootEffect, WriteIOEffect].}