Interval_traversal (Key_Start, Key_End): Traversing several key–value pairs in PMEKV

Search the key index tree in the device memory;   Find the LeadNode that Key_Start may appear;   Check whether the Key in the leaf node equals to or less than Key_Start;   If (exist the key >= Key_Start and Key < Key_End) {    Do {     Access the Value_pointer corresponding to this key;     Access the data corresponding to this Value_Pointer in the NVM device as value;   Return key–value pairs with this key and value;   If (exist the key unvisited in this LeadNode)      Move to the next key;     Else   Move to the first key in the next LeadNode;    }    While (Current key in this LeadNode <= Key_End)   }   Else    Return information that there is not the key–value pair with the key between Key_Start and Key_End;}