input: Write a function to explain how to use recursion to solve a given problem in Python. The function should return a string that provides a brief explanation of recursion, including how to break down problems and how to define a recursive function in Python.
  assert recursion_explanation()== "Recursion is a powerful technique for solving problems. It involves defining a problem in terms of itself. A recursion problem is solved by breaking it down into smaller problems, until the problem is small enough to be solved directly. The result from a smaller problem can then be combined with the result from the larger problem, until the original problem is solved. In Python, a recursive function is one that calls itself."
  assert recursion_explanation().startswith("Recursion is a powerful technique")==True
  assert "recursive function" in recursion_explanation()==True
  assert "calls itself" in recursion_explanation()==True
output: def recursion_explanation():
      return "Recursion is a powerful technique for solving problems. It involves defining a problem in terms of itself. A recursion problem is solved by breaking it down into smaller problems, until the problem is small enough to be solved directly. The result from a smaller problem can then be combined with the result from the larger problem, until the original problem is solved. In Python, a recursive function is one that calls itself."