code: def t_hexnumber(self, t):
          r'-?0[xX][0-9a-fA-F]+'
          t.value = int(t.value, base=16)
          t.type = 'NUMBER'
          return f t_hexnumber(self, t):
          r'-?0[xX][0-9a-fA-F]+'
          t.value = int(t.value, base=16)
          t.type = 'NUMBER'
          return t
docs: r'-?0[xX][0-9a-fA-F]+