input: Write a function to explain the concept of recursion in Python and how it can be used to solve a given problem. The function should describe recursion as a technique that involves defining a problem in terms of itself and breaking it down into smaller problems until a base case is reached. The function should also mention that in Python, a recursive function is one that calls itself.
  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."
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."