this_append_before for explicable ans abstract_polynom

pymath/calculus/explicable.py

@@ -61,6 +61,23 @@ class Explicable(Renderable):
             else:
                 return False
 
+    def this_append_before(self, steps):
+        """ Add steps at the beginning of self.steps
+
+        :param steps: list of steps that append before
+
+        >>> e = Explicable()
+        >>> s = ['eat', 'sleep']
+        >>> e.this_append_before(s)
+        >>> print(e.steps)
+        ['eat', 'sleep']
+        >>> s0 = ['cook']
+        >>> e.this_append_before(s0)
+        >>> print(e.steps)
+        ['cook', 'eat', 'sleep']
+        """
+        self.steps = steps + self.steps
+
 class Explicable_int(int, Explicable):
     """ An Explicable_int is an int which can be explain """
     isNumber = True