DATABASE_URL            URL pointing to the full metadata file
SAMPLE_DATABASE_URL     URL pointing to the sample metadata file, which
                        is smaller and for test, demonstration, and
                        vignette purposes only
get_SingleCellExperiment
                        Gets a SingleCellExperiment from curated
                        metadata
get_metadata            Gets the Curated Atlas metadata as a data
                        frame.
get_seurat              Given a data frame of HCA metadata, returns a
                        Seurat object corresponding to the samples in
                        that data frame
get_single_cell_experiment
                        Gets a SingleCellExperiment from curated
                        metadata
get_unharmonised_dataset
                        Returns unharmonised metadata for selected
                        datasets.
get_unharmonised_metadata
                        Returns unharmonised metadata for a metadata
                        query
