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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 isInstalledBuild(self):
 		""" 		Determines if the Engine is an Installed Build 		"""

		sentinelFile = os.path.join(self.getEngineRoot(), 'Engine', 'Build', 'InstalledBuild.txt')
		return os.path.exists(sentinelFile)