Flash video file (.flv)

def is_flv(file_path: str) -> bool:
    """Check if file is a valid FLV by magic bytes."""
    signature = bytes([0x46, 0x4C, 0x56])
    with open(file_path, "rb") as f:
        return f.read(3) == signature

function isFLV(buffer: Buffer): boolean {
  const signature = Buffer.from([0x46, 0x4C, 0x56]);
  return buffer.subarray(0, 3).equals(signature);
}

func IsFLV(data []byte) bool {
    signature := []byte{0x46, 0x4C, 0x56}
    if len(data) < 3 {
        return false
    }
    return bytes.Equal(data[:3], signature)
}