_source
├── instrument_model
├── library_layout/selection/source/strategy
├── platform
├── sample
│   ├── BioSample
│   ├── Published/Received/Status
│   ├── accession
│   ├── alias
│   ├── attributes (tag, value):
│   │   ├── BioSampleModel
│   │   ├── collection_date
│   │   ├── geo_loc_name
│   │   ├── identified_by
│   │   ├── isolation_source
│   │   ├── sample_type
│   │   └── strain
│   ├── center_name
│   ├── identifiers (id, namespace)*
│   ├── organism
│   ├── sample_accession
│   └── taxon_id
└── study
    ├── BioProject
    ├── LastMetaUpdate/LastUpdate/Published/Received
    ├── Status
    ├── abstract
    ├── accession
    ├── alias
    ├── center_name
    ├── identifiers (id, namespace*)
    ├── study_accession
    ├── study_type
    └── title
