def read_samples(fn):
    """Read samples from the header of a GFF file.

    Args:
        *fn(str)*: GFF file to read.

    Returns:
        *(list)*: character list with sample names.
    """
    with open(fn) as inh:
        for line in inh:
            if line.startswith("## COLDATA"):
                return line.strip().split(": ")[1].strip().split(",")
    raise ValueError("%s doesn't contain COLDATA header." % fn)