Some fixes in Python level (#532)

Author: densmirn

dpnp/dpnp_iface_arraycreation.py

@@ -115,12 +115,12 @@ def arange(start, stop=None, step=1, dtype=None):
     [3, 5]
 
     """
-    if use_origin_backend():
+    if not use_origin_backend():
         if not isinstance(start, int):
             pass
-        if not isinstance(stop, int) or stop is not None:
+        elif not isinstance(stop, int) or stop is not None:
             pass
-        if not isinstance(step, int) or step is not None:
+        elif not isinstance(step, int) or step is not None:
             pass
         else:
             if dtype is None:

dpnp/dpnp_iface_trigonometric.py

@@ -514,7 +514,7 @@ def exp(x1):
     [1.0, 2.718281828, 7.389056099]
 
     """
-    if use_origin_backend(x1):
+    if not use_origin_backend(x1):
         if not isinstance(x1, dparray):
             pass
         else:
@@ -662,7 +662,7 @@ def log(x1):
     [0.0, 1.0, 2.0, -inf]
 
     """
-    if use_origin_backend(x1):
+    if not use_origin_backend(x1):
         if not isinstance(x1, dparray):
             pass
         else: