Fix 6 Flake8 issues (#6541)

* F541

* F821

* F841

* E741

* E302

* E722

* Apply suggestions from code review

* Update general.py

* Update datasets.py

* Update export.py

* Update plots.py

* Update plots.py

Co-authored-by: Glenn Jocher <glenn.jocher@ultralytics.com>

utils/torch_utils.py

@@ -49,7 +49,7 @@ def git_describe(path=Path(__file__).parent):  # path must be a directory
     s = f'git -C {path} describe --tags --long --always'
     try:
         return subprocess.check_output(s, shell=True, stderr=subprocess.STDOUT).decode()[:-1]
-    except subprocess.CalledProcessError as e:
+    except subprocess.CalledProcessError:
         return ''  # not a git repository
 
 
@@ -59,7 +59,7 @@ def device_count():
     try:
         cmd = 'nvidia-smi -L | wc -l'
         return int(subprocess.run(cmd, shell=True, capture_output=True, check=True).stdout.decode().split()[-1])
-    except Exception as e:
+    except Exception:
         return 0
 
 
@@ -124,7 +124,7 @@ def profile(input, ops, n=10, device=None):
             tf, tb, t = 0, 0, [0, 0, 0]  # dt forward, backward
             try:
                 flops = thop.profile(m, inputs=(x,), verbose=False)[0] / 1E9 * 2  # GFLOPs
-            except:
+            except Exception:
                 flops = 0
 
             try:
@@ -135,7 +135,7 @@ def profile(input, ops, n=10, device=None):
                     try:
                         _ = (sum(yi.sum() for yi in y) if isinstance(y, list) else y).sum().backward()
                         t[2] = time_sync()
-                    except Exception as e:  # no backward method
+                    except Exception:  # no backward method
                         # print(e)  # for debug
                         t[2] = float('nan')
                     tf += (t[1] - t[0]) * 1000 / n  # ms per op forward