function fromRawMappings(
  modules: $ReadOnlyArray<{
    +map: ?Array<MetroSourceMapSegmentTuple>,
    +functionMap: ?FBSourceFunctionMap,
    +path: string,
    +source: string,
    +code: string,
    +isIgnored: boolean,
    +lineCount?: number,
  }>,
  offsetLines: number = 0,
): Generator {
  let generator: void | Generator;
  fromRawMappingsImpl(
    true,
    g => {
      generator = g;
    },
    modules,
    offsetLines,
  );
  if (generator == null) {
    throw new Error('Expected fromRawMappingsImpl() to finish synchronously.');
  }
  return generator;
}
Creates a source map from modules with "raw mappings", i.e. an array of
tuples with either 2, 4, or 5 elements:
generated line, generated column, source line, source line, symbol name.
Accepts an `offsetLines` argument in case modules' code is to be offset in
the resulting bundle, e.g. by some prefix code.