def extract_crs(da):
    """
    Takes an xarray Dataset pulled from opendatacube and extracts crs metadata
    if exists. Returns None if not found.
    
    Parameters
    ----------
    da: xarray Dataset
        A single- or multi-dimensional array containing (or not) crs metadata.

    Returns
    -------
    crs: str
        A crs object.
    """
    
    # notify user
    print('Beginning extraction of CRS metadata.')
    try:
        # notify user
        print('> Extracting CRS metadata.')
        
        # extract crs metadata
        crs = da.geobox.crs
        
        # notify user
        print('> Success!\n')
        
    except:
        # notify user
        print('> No CRS metadata found. Returning None.\n')
        crs = None       
    
    return crs