code: def Override(self, overrides):
          
          if not overrides: return self
          o = copy_non_reserved_keywords(overrides)
          if not o: return self
          overrides = {}
          merges = None
          for key, value in o.items():
              if key == 'parse_flags':
                  merges = value
              else:
                  overrides[key] = SCons.Subst.scons_subst_once(value, self, key)
          env = OverrideEnvironment(self, overrides)
          if merges: env.MergeFlags(merges)
          return env
docs: Produce a modified environment whose variables are overridden by
          the overrides dictionaries.  "overrides" is a dictionary that
          will override the variables of this environment.
  
          This function is much more efficient than Clone() or creating
          a new Environment because it doesn't copy the construction
          environment dictionary, it just wraps the underlying construction
          environment, and doesn't even create a wrapper object if there
          are no overrides.