code: def _grid_coordinates(side):
      M = side**2
      x = np.linspace(0, 1, side, dtype=np.float32)
      y = np.linspace(0, 1, side, dtype=np.float32)
      xx, yy = np.meshgrid(x, y)
      z = np.empty((M, 2), np.float32)
      z[:, 0] = xx.reshape(M)
      z[:, 1] = yy.reshape(M)
      return z
  
file_path: spektral/spektral/datasets/mnist.py
imports: import numpy
  import scipy.sparse
  from sklearn.neighbors import kneighbors_graph
  from tensorflow.keras.datasets import mnist
  from spektral.data import Dataset, Graph
label_desc: Use image node_id 1 for calling a global function with example usage: _grid_coordinates(side) and returns: z