contract Hello2020 is
  NFTokenMetadata,
  Ownable
{

  /**
   * @dev Contract constructor. Sets metadata extension `name` and `symbol`.
   */
  constructor()
    public
  {
    nftName = "Hello 2020";
    nftSymbol = "Hello2020";
  }

  /**
   * @dev Mints a new NFT.
   * @param _to The address that will own the minted NFT.
   * @param _tokenId of the NFT to be minted by the msg.sender.
   * @param _uri String representing RFC 3986 URI.
   */
  function mint(
    address _to,
    uint256 _tokenId,
    string calldata _uri
  )
    external
    onlyOwner
  {
    super._mint(_to, _tokenId);
    super._setTokenUri(_tokenId, _uri);
  }

}
/**
 * @dev This is an example contract implementation of NFToken with metadata extension.
 */
function mint(
  address _to,
  uint256 _tokenId,
  string calldata _uri
)
  external
  onlyOwner
{
  super._mint(_to, _tokenId);
  super._setTokenUri(_tokenId, _uri);
}

/**
 * @dev Mints a new NFT.
 * @param _to The address that will own the minted NFT.
 * @param _tokenId of the NFT to be minted by the msg.sender.
 * @param _uri String representing RFC 3986 URI.
 */