add sage extensions

classes/helpers/sage_extensions.py

+from __future__ import absolute_import
+from sage.all import random_matrix, random_vector, random
+
+
+def random_invertible_matrix(finite_field, n):
+    matrix = random_matrix(finite_field, n)
+
+    while not matrix.is_invertible():
+        matrix = random_matrix(finite_field, n)
+
+    return matrix
+
+
+def random_value(finite_field):
+    return random_vector(finite_field, 1)[0]
+
+
+def random_between(j, k):
+    a = int(random() * (k - j + 1)) + j
+    return a