write an instruction file for a modflow head observation file

    Parameters
    ----------
    hob_file : str
        modflow hob file

    Returns
    -------
    df : pandas.DataFrame
        pandas DataFrame with control file observation information

def modflow_hob_to_instruction_file(hob_file):
    """write an instruction file for a modflow head observation file

    Parameters
    ----------
    hob_file : str
        modflow hob file

    Returns
    -------
    df : pandas.DataFrame
        pandas DataFrame with control file observation information
    """

    hob_df = pd.read_csv(hob_file,delim_whitespace=True,skiprows=1,
                         header=None,names=["simval","obsval","obsnme"])

    hob_df.loc[:,"obsnme"] = hob_df.obsnme.apply(str.lower)
    hob_df.loc[:,"ins_line"] = hob_df.obsnme.apply(lambda x:"l1 !{0:s}!".format(x))
    hob_df.loc[0,"ins_line"] = hob_df.loc[0,"ins_line"].replace('l1','l2')

    ins_file = hob_file + ".ins"
    f_ins = open(ins_file, 'w')
    f_ins.write("pif ~\n")
    f_ins.write(hob_df.loc[:,["ins_line"]].to_string(col_space=0,
                                                     columns=["ins_line"],
                                                     header=False,
                                                     index=False,
                                                     formatters=[SFMT]) + '\n')
    hob_df.loc[:,"weight"] = 1.0
    hob_df.loc[:,"obgnme"] = "obgnme"
    f_ins.close()
    return hob_df