Write a Python program to check if a set is a subset of another set. The function should return True if the first set is a subset of the second, False otherwise.
Example 1:
Input: {1, 2, 3}, {1, 2, 3, 4, 5}
Output: True
Example 2:
Input: {1, 2, 3, 4, 5}, {1, 2, 3}
Output: False