input: Write a function to explain how recursion works in Python and how it can be used to solve problems. The function should discuss the concept of defining a problem in terms of itself, breaking down the problem into smaller subproblems, and combining results from smaller problems to solve the original problem. Additionally, mention that in Python, a recursive function calls itself to solve the problem.
  assert explain_recursion()=="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."
output: def explain_recursion():
      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."