docs: 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