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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 _op(self, operation, other, *allowed):
 		"""A basic operation operating on a single value."""

		
		f = self._field
		
		if self._combining:  # We are a field-compound query fragment, e.g. (Foo.bar & Foo.baz).
			return reduce(self._combining,
					(q._op(operation, other, *allowed) for q in f))  # pylint:disable=protected-access
		
		# Optimize this away in production; diagnosic aide.
		if __debug__ and _complex_safety_check(f, {operation} | set(allowed)):  # pragma: no cover
			raise NotImplementedError("{self!r} does not allow {op} comparison.".format(self=self, op=operation))
		
		if other is not None:
			other = f.transformer.foreign(other, (f, self._document))
		
		return Filter({self._name: {operation: other}})