Create a frequency counter that counts how many times each element appears in a list of integers. Return a map where the keys are the unique integers from the list and the values are the counts of their occurrences.
Examples:
Input: numbers = [1, 2, 3, 1, 2, 1]
Output: {1: 3, 2: 2, 3: 1}
Explanation: 1 appears 3 times, 2 appears 2 times, 3 appears once
Input: numbers = [5, 5, 5, 5]
Output: {5: 4}
Explanation: 5 appears 4 times
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