code: function (oInstance, sMetaPath, mTypeForMetaPath) {
  			var aFilters = [],
  				sKey,
  				mKey2Value = _Helper.getKeyProperties(oInstance, sMetaPath, mTypeForMetaPath);
  
  			if (!mKey2Value) {
  				return undefined;
  			}
  			for (sKey in mKey2Value) {
  				aFilters.push(sKey + " eq " + mKey2Value[sKey]);
  			}
  
  			return aFilters.join(" and ");
  		}
docs: Returns a filter identifying the given instance via its key properties.
  
  @param {object} oInstance
  Entity instance runtime data
  @param {string} sMetaPath
  The absolute meta path of the given instance
  @param {object} mTypeForMetaPath
  Maps meta paths to the corresponding entity or complex types
  @returns {string}
  A filter using key properties, e.g. "Sector eq 'DevOps' and ID eq 42)", or undefined,
  if at least one key property is undefined
  @throws {Error}
  In case the entity type has no key properties according to metadata