input: Write a python function to perform PCA transformation on a given dataset using sklearn.
  assert pca_transform([[1, 2], [3, 4], [5, 6]]) is not None
  assert pca_transform([[7, 8], [9, 10], [11, 12]]).shape == (3, 2)
  assert isinstance(pca_transform([[13, 14], [15, 16], [17, 18]]), np.ndarray)
output: def pca_transform(data):
      from sklearn.decomposition import PCA
      import numpy as np
      
      pca = PCA()
      transformed_data = pca.fit_transform(data)
      return transformed_data