code: def get_posix(self, i):
          
  
          index = i.index
          value = ['[']
          try:
              c = next(i)
              if c != ':':
                  raise ValueError('Not a valid property!')
              else:
                  value.append(c)
                  c = next(i)
                  if c == '^':
                      value.append(c)
                      c = next(i)
                  while c != ':':
                      if c not in _PROPERTY:
                          raise ValueError('Not a valid property!')
                      if c not in _PROPERTY_STRIP:
                          value.append(c)
                      c = next(i)
                  value.append(c)
                  c = next(i)
                  if c != ']' or not value:
                      raise ValueError('Unmatched ]')
                  value.append(c)
          except Exception:
              i.rewind(i.index - index)
              value = []
          return ''.join(value) if value else None
docs: Get POSIX.