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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 warmup(self):
 """ initialize variables necessary to perform a sprinter action """

        self.logger.debug("Warming up...")

        try:
            if not isinstance(self.source, Manifest) and self.source:
                self.source = load_manifest(self.source)
            if not isinstance(self.target, Manifest) and self.target:
                self.target = load_manifest(self.target)
            self.main_manifest = self.target or self.source
        except lib.BadCredentialsException:
            e = sys.exc_info()[1]
            self.logger.error(str(e))
            raise SprinterException("Fatal error! Bad credentials to grab manifest!")

        if not getattr(self, 'namespace', None):
            if self.target:
                self.namespace = self.target.namespace
            elif not self.namespace and self.source:
                self.namespace = self.source.namespace
            else:
                raise SprinterException("No environment name has been specified!")

        self.directory_root = self.custom_directory_root

        if not self.directory:
            if not self.directory_root:
                self.directory_root = os.path.join(self.root, self.namespace)

            self.directory = Directory(self.directory_root,
                                       shell_util_path=self.shell_util_path)

        if not self.injections:
            self.injections = Injections(wrapper="%s_%s" % (self.sprinter_namespace.upper(),
                                                            self.namespace),
                                         override="SPRINTER_OVERRIDES")
        if not self.global_injections:
            self.global_injections = Injections(wrapper="%s" % self.sprinter_namespace.upper() + "GLOBALS",
                                                override="SPRINTER_OVERRIDES")
        # append the bin, in the case sandboxes are necessary to
        # execute commands further down the sprinter lifecycle
        os.environ['PATH'] = self.directory.bin_path() + ":" + os.environ['PATH']
        self.warmed_up = True