add import statement in doctest

Author: dhruv-pharasi

machine_learning/logistic_regression.py

@@ -113,6 +113,7 @@ def log_likelihood(x, y, weights):
         weights (ndarray): shape (n_features,) parameter vector
 
     Examples:
+    >>> import numpy as np
     >>> x = np.array([[0, 0, 0]])
     >>> y = np.array([0, 0, 0])
     >>> w = np.array([0, 0, 0])
@@ -156,6 +157,7 @@ def logistic_reg(alpha, x, y, max_iterations=70000):
         Learned weight vector after optimization.
 
     Examples:
+    >>> import numpy as np
     >>> alpha = 0.001
     >>> x = np.ones((2, 2))
     >>> y = np.ones(2)