Function extract_variables 

pub fn extract_variables(
    group: &Group,
    dimensions: &[NcDimension],
    dim_addr_map: &HashMap<u64, NcDimension>,
    metadata_mode: NcMetadataMode,
) -> Result<Vec<NcVariable>>

Extract variables from an HDF5 group.

Dimension-only scale datasets are internal metadata. Coordinate variables are also dimension scales, so they are preserved as NcVariables.

dim_addr_map maps dimension-scale dataset addresses to their NcDimension, used to resolve DIMENSION_LIST object references.