Eliminate All Unneeded Else / Elif statements to Increase Readability

[justincpresley]

Found these places via the tool codefactor. There are other issues that it detects, but I left those open as there could be different ways to solve them.

[zjkmxy]

• Some of them are valid (such as the isinstance one). Thank you.
• Personally I think extra else improves readability. For example,

  if a > 0:
  return "Positive"
  else:
  return "Non-Positive"

  is better than

  if a > 0:
  return "Positive"
  return "Non-Positive"

  because "Positive" and "Non-Positive" are actually belonging to the same layer -- there is no reason to let them have different indents just because of the return.

• For the sake of command-line tools, an extra empty line is preferable. My PyCharm always reminds me to add one. However, your tools somehow eliminates all such lines.

I don't think I will merge this PR. But I will consider fix some of them.