<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def vcf_as_df(fn):
 """ Read VCF file into pandas DataFrame. Parameters: fn : str Path to VCF file. Returns ------- df : pandas.DataFrame The VCF file as a data frame. Note that all header information is thrown away. """

    header_lines = 0
    with open(fn, 'r') as f:
        line = f.readline().strip()
        header_lines += 1
        while line[0] == '#':
            line = f.readline().strip()
            header_lines += 1
    
    header_lines -= 2
    df = pd.read_table(fn, skiprows=header_lines, header=0)
    df.columns = ['CHROM'] + list(df.columns[1:])
    return df