docker-compose up --build -d で ERROR: The Compose file './docker-compose.yml' is invalid because　が出た時

WARNING: The JUPYTER_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The MINIO_ROOT_USER variable is not set. Defaulting to a blank string.
WARNING: The MINIO_ROOT_PASSWORD variable is not set. Defaulting to a blank string.
WARNING: The MLFLOW_HOST_PORT variable is not set. Defaulting to a blank string.
WARNING: The MYSQL_USER variable is not set. Defaulting to a blank string.
WARNING: The MYSQL_PASSWORD variable is not set. Defaulting to a blank string.
WARNING: The MYSQL_DATABASE variable is not set. Defaulting to a blank string.
WARNING: The MYSQL_ROOT_PASSWORD variable is not set. Defaulting to a blank string.
WARNING: The MINIO_HOST_PORT variable is not set. Defaulting to a blank string.
ERROR: The Compose file './docker-compose.yml' is invalid because:
services.mlflow.ports contains an invalid type, it should be a number, or an object
services.jupyter.ports contains an invalid type, it should be a number, or an object
services.minio.ports contains an invalid type, it should be a number, or an object

原因：
ディレクトリ構成が間違っている OR ファイルが足りていないことがある。
例えば、隠れファイル(ls -laコマンドで表示される)の「.env」など忘れがち。