docs: def get_file_extension(self, filepath):
          """
          This method check mimetype to define file extension.
          If it can't, it use original-format metadata.
          """
          mtype = magic.from_file(filepath, mime=True)
          if type(mtype) == bytes:
              mtype = mtype.decode("utf-8")
  
          if mtype == "audio/mpeg":
              ext = ".mp3"
          elif mtype == "audio/x-wav":
              ext = ".wav"
          else:
              ext = "." + self.get("original-format")
          return ext