Convert dict to string

Convert dict to string.

Sample Code:

def objStr(d):
# Enter your logic here...

Examples:

Input: {'lang':'Python'}
Output: {'lang':'Python'}
Explanation: Both input and output looks the same, but they are different in data types.

Input: {'skill':None}
Output: {'skill':null}
Explanation: None is a falsy value. Therefore it returns null.