public static boolean hasMimeType(String mimeType) {
    return sMimeTypeToExtensionMap.containsKey(mimeType) || sMimeTypeMap.hasMimeType(mimeType);
  }
Wrapper around the system's {@link MimeTypeMap} that also handles types it doesn't support.
fbcore/src/main/java/com/facebook/common/media/MimeTypeMapWrapper.java