docs: def find_one(cls, pattern, string, flags=0):
          """JS-like match object. Use index number to get groups, if not match or no group, will return ''.
  
          Basic Usage::
  
              >>> from torequests.utils import find_one
              >>> string = "abcd"
              >>> find_one("a.*", string)
              <torequests.utils.RegMatch object at 0x0705F1D0>
              >>> find_one("a.*", string)[0]
              'abcd'
              >>> find_one("a.*", string)[1]
              ''
              >>> find_one("a(.)", string)[0]
              'ab'
              >>> find_one("a(.)", string)[1]
              'b'
              >>> find_one("a(.)", string)[2] or "default"
              'default'
              >>> import re
              >>> item = find_one("a(B)(C)", string, flags=re.I | re.S)
              >>> item
              <torequests.utils.RegMatch object at 0x0705F1D0>
              >>> item[0]
              'abc'
              >>> item[1]
              'b'
              >>> item[2]
              'c'
              >>> item[3]
              ''
              >>> # import re
              >>> # re.findone = find_one
              >>> register_re_findone()
              >>> re.findone('a(b)', 'abcd')[1] or 'default'
              'b'
  
          """
          item = re.search(pattern, string, flags=flags)
          return cls(item)