input: Write a python function to repeat a string a given number of times.
  assert repeat_string("Abstract", 3) == "AbstractAbstractAbstract"
  assert repeat_string("Hello", 2) == "HelloHello"
  assert repeat_string("Test", 1) == "Test"
  assert repeat_string("Python", 0) == ""
output: def repeat_string(s: str, n: int) -> str:
      return s * n