code: func Sources(dst io.Writer, from, to schemalex.SchemaSource, options ...Option) error {
  	var buf bytes.Buffer
  	if err := from.WriteSchema(&buf); err != nil {
  		return errors.Wrapf(err, `failed to retrieve schema from "from" source %s`, from)
  	}
  	fromStr := buf.String()
  	buf.Reset()
  
  	if err := to.WriteSchema(&buf); err != nil {
  		return errors.Wrapf(err, `failed to retrieve schema from "to" source %s`, to)
  	}
  	return Strings(dst, fromStr, buf.String(), options...)
  }
docs: // Files compares contents from two sources and generates a series
  // of statements to migrate from the old one to the new one,
  // writing the result to `dst`