code: def rename_sequences(self, mapping, new_path=None, in_place=False):
          
          # Where is the new file #
          if new_path is None: new_fasta = self.__class__(new_temp_path())
          else:                new_fasta = self.__class__(new_path)
          # Do it #
          new_fasta.create()
          for seq in self:
              new_name = mapping[seq.description]
              nucleotides = str(seq.seq)
              new_fasta.add_str(nucleotides, new_name)
          new_fasta.close()
          # Return #
          if in_place:
              os.remove(self.path)
              shutil.move(new_fasta, self.path)
              return self
          else: return new_fasta
docs: Will rename all sequences in the current fasta file using
          the mapping dictionary also provided. In place or at a new path.