input: Write a function to create a Python class called Rectangle to represent a two-dimensional rectangle with a length and width. Implement an initializer to set the length and width of the rectangle, and implement a method to calculate the area. If the input is a valid integer or float for length and width, the area should be returned as an integer or float. If the input is invalid, an appropriate error message should be returned.
  
  class Rectangle:
      def __init__(self, length, width):
          self.length = length
          self.width = width
  
      def area(self):
          return self.length * self.width
  
  assert Rectangle(5, 10).area() == 50
  assert Rectangle(7.5, 3).area() == 22.5
  assert Rectangle(0, 10).area() == 0
  assert Rectangle(-5, 10).area() == -50
output: class Rectangle:
      def __init__(self, length, width):
          if not isinstance(length, (int, float)) or not isinstance(width, (int, float)):
              raise ValueError("Length and width must be integers or floats")
          if length < 0 or width < 0:
              raise ValueError("Length and width must be non-negative")
          self.length = length
          self.width = width
  
      def area(self):
          return self.length * self.width