import io
import gzip


def decompress_block(byte_stream):
    """Interpret a byte string as a BGZF block and return its decompressed
    contents.

    BGZF format is gunzip compatible, so the gzip module can perform the
    decompression.

    Args:
        byte_stream (bytes): Complete BGZF block to be decompressed.

    Returns:
        Bytes representing the decompressed block.
    """
    byte_stream = io.BytesIO(byte_stream)
    return gzip.GzipFile(fileobj=byte_stream).read()