def populate_unpaired_line(d_vals, f_f_header, missing_val=None):
if missing_val is None:<EOL><INDENT>raise MissingValueError("<STR_LIT>" +<EOL>"<STR_LIT>")<EOL><DEDENT>if f_f_header is not None:<EOL><INDENT>f_f_flds = [dict(zip(f_f_header, [missing_val] * len(f_f_header)))]<EOL><DEDENT>else:<EOL><INDENT>assert(len(d_vals) > <NUM_LIT:0>)<EOL>f_f_num_cols = len(d_vals[d_vals.keys()[<NUM_LIT:0>]][<NUM_LIT:0>])<EOL>f_f_flds = [[missing_val] * f_f_num_cols]<EOL><DEDENT>return f_f_flds<EOL>
used when a value in d_vals doesn't match anything in the other file.

:return: a dictionary, indexed by key value, with the correct missing values
         populated for the other file.