docs: function parseElemMatch(operand) {
      if(fieldOperand(operand)) {
          var parts = []
          for(var operator in operand) {
              var innerOperand = operand[operator]
              parts.push(parseFieldOperator(undefined, operator, innerOperand))
          }
          return {parts: parts, implicitField: true}
      } else {          // non-field operators ( stuff like {a:5} or {$and:[...]} )
          return {parts: parseQuery(operand), implicitField: false}
      }
  }