PHP Compatibility Issues

I ran PHP Compatibility Checker plugin (against PHP 7.3) and it gave 3 warnings and 1 error regarding your plugin.

FILE: /var/www/html/wp-content/plugins/machete/inc/utils/frontend-functions.php
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FOUND 1 ERROR AND 3 WARNINGS AFFECTING 4 LINES
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  17 | WARNING | Closures / anonymous functions only have access to $this if used within a class or when bound to an object using bindTo(). Please verify.
  66 | WARNING | Closures / anonymous functions only have access to $this if used within a class or when bound to an object using bindTo(). Please verify.
  84 | WARNING | Closures / anonymous functions only have access to $this if used within a class or when bound to an object using bindTo(). Please verify.
 104 | ERROR   | "$this" can no longer be used in a plain function or method since PHP 7.1.
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Please look into this.