code: public static List<String> extractBaseImages(File dockerFile, FixedStringSearchInterpolator interpolator) throws IOException {
          List<String[]> fromLines = extractLines(dockerFile, "FROM", interpolator);
          LinkedList<String> result = new LinkedList<>();
          for (String[] fromLine :  fromLines) {
              if (fromLine.length > 1) {
                  result.add(fromLine[1]);
              }
          }
          return result;
      }
docs: Extract the base images from a dockerfile. All lines containing a <code>FROM</code> is
  taken.
  
  @param dockerFile file from where to extract the base image
  @param interpolator interpolator for replacing properties
  @return LinkedList of base images name or empty collection if none is found.