code: def pair_for_message_hash(self, signature, msg_hash):
          
  
          # Decode base64 and a bitmask in first byte.
          is_compressed, recid, r, s = self._decode_signature(signature)
  
          # Calculate the specific public key used to sign this message.
          y_parity = recid & 1
          q = self._generator.possible_public_pairs_for_signature(msg_hash, (r, s), y_parity=y_parity)[0]
          if recid > 1:
              order = self._generator.order()
              q = self._generator.Point(q[0] + order, q[1])
          return q, is_compressed
docs: Take a signature, encoded in Base64, and return the pair it was signed by.
          May raise EncodingError (from _decode_signature)