code: func (c *Callbacks) OnCDOTAUserMsg_PlayerMMR(fn func(*dota.CDOTAUserMsg_PlayerMMR) error) {
  	c.onCDOTAUserMsg_PlayerMMR = append(c.onCDOTAUserMsg_PlayerMMR, fn)
  }
docs: // OnCDOTAUserMsg_PlayerMMR registers a callback for EDotaUserMessages_DOTA_UM_PlayerMMR