Will rename all sequences in the current fasta file using
        the mapping dictionary also provided. In place or at a new path.

def rename_sequences(self, mapping, new_path=None, in_place=False):
        """Will rename all sequences in the current fasta file using
        the mapping dictionary also provided. In place or at a new path."""
        # 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