docs: def parse_phones(self):
          """Parse TextGrid phone intervals.
          
          This method parses the phone intervals in a TextGrid to extract each
          phone and each phone's start and end times in the audio recording. For
          each phone, it instantiates the class Phone(), with the phone and its
          start and end times as attributes of that class instance.
          
          """
          phones = []
          
          for i in self.phone_intervals:
              start = float(i[i.index('xmin = ')+7:
                              i.index('xmin = ')+12].strip('\t').strip('\n'))
              end = float(i[i.index('xmax = ')+7:
                            i.index('xmax = ')+12].strip('\t').strip('\n'))
              phone = i[i.index('\"')+1:i.index("$")]
              phones.append(Phone(phone, start, end))
              
          return phones