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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_jar_fp(self):
 """Returns the full path to the JAR file. If the JAR file cannot be found in the current directory and the environment variable RDP_JAR_PATH is not set, returns None. """

        # handles case where the jar file is in the current working directory
        if os.path.exists(self._command):
            return self._command
        # handles the case where the user has specified the location via
        # an environment variable
        elif 'RDP_JAR_PATH' in environ:
            return getenv('RDP_JAR_PATH')
        else:
            return None