code: def p_variable(self, p):
          
          p[0] = [_Segment(_BINDING, p[2])]
          if len(p) > 4:
              p[0].extend(p[4])
          else:
              p[0].append(_Segment(_TERMINAL, '*'))
              self.segment_count += 1
          p[0].append(_Segment(_END_BINDING, ''))
docs: variable : LEFT_BRACE LITERAL EQUALS unbound_segments RIGHT_BRACE
                      | LEFT_BRACE LITERAL RIGHT_BRACE