function logical(sOp, oLeft, oRight) {
			return {
				type: Type.Logical,
				op: sOp,
				left: oLeft,
				right: oRight
			};
		}
Returns an AST for the filter.

@param {boolean} bIncludeOrigin Whether the origin should be included in the AST

@returns {object} An AST for the filter
@throws {Error} If this filter has no or an unknown operator

@private