Implement a function that extracts all keys from a map and returns them as a sorted list. Return an empty list for null or empty maps.
Examples:
Input: map = {'a': 1, 'c': 3, 'b': 2}
Output: ['a', 'b', 'c']
Explanation: The keys 'a', 'b', 'c' are extracted and sorted alphabetically
Input: map = {'one': 1, 'two': 2, 'three': 3}
Output: ['one', 'three', 'two']
Explanation: The keys 'one', 'three', 'two' are extracted and sorted alphabetically
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