0x8n A map containing "n" key/value pairs -> 0x81 introduces a single key/value pair

b101XXXXX : A string where XXXXX is the string length -> 0xA2 introudces a 2 byte string

0xC6 followed by a 32-bit value N introduces an array of bytes of size N

0x70 0x62 "pb"

So it roughly corresponds to

  {"pb": <protobuf data> }