input: Write a function that removes all negative numbers from a given matrix. The function should return the matrix with all negative numbers replaced by zeroes.
  import numpy as np
  def filter_out_negative(matrix):
    matrix = np.array(matrix)
    matrix[matrix < 0] = 0
    return matrix
  
  assert np.array_equal(filter_out_negative([[-1, 2, -3], [-4, 5, 6], [-7, 8, 9]]), [[0, 2, 0], [0, 5, 6], [0, 8, 9]])
  assert np.array_equal(filter_out_negative([[1, -2, 3], [-4, 5, -6], [7, -8, 9]]), [[1, 0, 3], [0, 5, 0], [7, 0, 9]])
  assert np.array_equal(filter_out_negative([[], [], []]), [[], [], []])
  assert np.array_equal(filter_out_negative([[0, 0, 0], [0, 0, 0], [0, 0, 0]]), [[0, 0, 0], [0, 0, 0], [0, 0, 0]])
output: 
  import numpy as np
  def filter_out_negative(matrix):
    matrix = np.array(matrix)
    matrix[matrix < 0] = 0
    return matrix
  