code: def escape_string_json(st):
      
      ret = []
      c = 0
      ln = len(st)
  
      escape_chmap = {
          b'\b': b'b',
          b'\f': b'f',
          b'\n': b'n',
          b'\r': b'r',
          b'\t': b't',
          b'\\': b'\\',
          b'\"': b'"',
          b'\/': b'/'
      }
  
      while c < ln:
          ch = st[c:c+1]
          if ch in escape_chmap:
              ret.append(b'\\' + escape_chmap[ch])
          elif ord(ch) < 0x20:
              ret.append(b'\\u%04X' % ord(ch))
          else:
              ret.append(ch)
          c += 1
      return b''.join(ret)
docs: Escaping string for json
      /Users/dusanklinec/workspace/monero/external/rapidjson/writer.h
      :param st:
      :return: