code: function getDepositAddressBySupernodeAddress(conn, supernodeAddress, cb){
      var conn = conn || db;
      if(!validationUtils.isNonemptyString(supernodeAddress))
          return cb("param supernodeAddress is null or empty string");
      if(!validationUtils.isValidAddress(supernodeAddress))
          return cb("param supernodeAddress is not a valid address");
  
      conn.query("SELECT deposit_address FROM supernode WHERE address = ?", [supernodeAddress], 
          function(rows) {
              if (rows.length !== 1 )
                  return cb("deposit address is not found when getDepositAddressBySupernodeAddress " + supernodeAddress);
              cb(null, rows[0].deposit_address);
      });
  }
docs: Returns deposit address by supernode address.
  
  @param	{obj}	    conn      if conn is null, use db query, otherwise use conn.
  @param   {String}    supernodeAddress
  @param   {function}	cb( err, deposit_address ) callback function
  If depositAddress is invalid, then returns err "invalid address".
  If can not find the address, then returns err "deposit address not found".