# Aufgabe
Implement the Mean Squared Error (MSE) loss function using numpy.

# Prompt
Your task is to generate python code to solve the following problem. The generated code must be placed between the ```python and ```, and only one code block is allowed: 
Implement the Mean Squared Error (MSE) loss function using numpy.

You need to follow the function names or class names in the test cases. The generated code should not contain any test cases: 
class Testmean_squared_error:
    def test_mean_squared_error_1(self):
        y_true = np.array([1, 2, 3, 4, 5])
        y_pred = np.array([1, 2, 3, 4, 5])
        assert mean_squared_error(y_true, y_pred) == 0.0