def generate_header(sample_name):
    """Function for generating the header for output VCF file.

    Args:
        sample_name (str): Name of the sample.

    Returns:
        str: Header for the VCF file.
    """
    fin = open("header", "rt")
    data = fin.read()
    data = data.replace('SAMPLENAME', sample_name)
    fin.close()
    return data+"\n"