def get_mol(chebi_id):
    '''Returns mol'''
    chebi_id_regexp = '^\\d+\\,' + str(chebi_id) + '\\,.*'
    mol_file_end_regexp = '\",mol,\\dD'
    this_structure = []

    filename = get_file('structures.csv.gz')

    with io.open(filename, 'r', encoding='cp1252') as textfile:
        in_chebi_id = False

        next(textfile)

        for line in textfile:
            if in_chebi_id or line[0].isdigit():
                if re.match(chebi_id_regexp, line) \
                    and int(line.split(',')[0]) \
                        in __get_default_structure_ids():
                    tokens = line.strip().split(',')
                    in_chebi_id = True
                    this_structure = []
                    this_structure.append(','.join(tokens[2:])
                                          .replace('\"', ''))
                    this_structure.append('\n')
                elif in_chebi_id:
                    if re.match(mol_file_end_regexp, line):
                        tokens = line.strip().split(',')
                        this_structure.append(tokens[0].replace('\"', ''))
                        return Structure(''.join(this_structure),
                                         Structure.mol,
                                         int(tokens[2][0]))
                    else:
                        # In Molfile:
                        this_structure.append(line)

    return None