human
Solve the following python programming problem given the following code:
def checkBuildRequirements(self, cfg, sourceVersion, raiseError = True) : 
    ' Checks to see if the build requirements for the recipe
            are installed
        ' 
    def _filterBuildReqsByVersionStr(versionStr, troves) : 
        if (not versionStr) : 
            return troves 
versionMatches = [] 
        if (versionStr.find ('@') == (- 1)) : 
            if (versionStr.find (':') == (- 1)) : 
                log.warning ('Deprecated buildreq format.  Use  foo=:tag, not foo=tag') 
                versionStr = (':' + versionStr) 
for trove in troves : 
            labels = trove.getVersion ().iterLabels () 
            if (versionStr [0] == ':') : 
                branchTag = versionStr [1 :] 
                branchTags = [x.getLabel () for x in labels] 
                if (branchTag in branchTags) : 
                    versionMatches.append (trove) 
else : 
                branchNames = [] 
                for label in labels : 
                    branchNames.append (('@%s:%s' % (label.getNamespace (), label.getLabel ()))) 
if (versionStr in branchNames) : 
                    versionMatches.append (trove) 
return versionMatches 
def _filterBuildReqsByFlavor(flavor, troves) : 
        troves.sort (key = (lambda x : x.getVersion ())) 
        if (flavor is None) : 
            return troves [(- 1)] 
for trove in troves : 
            troveFlavor = trove.getFlavor () 
            if troveFlavor.stronglySatisfies (flavor) : 
                return trove 
def _matchReqs(reqList, db) : 
        reqMap = { 
            
} 
        missingReqs = [] 
        for buildReq in reqList : 
            (name, versionStr, flavor) = cmdline.parseTroveSpec (buildReq) 
            troves = db.trovesByName (name) 
            troves = db.getTroves (troves) 
            versionMatches = _filterBuildReqsByVersionStr (versionStr, troves) 
            if (not versionMatches) : 
                missingReqs.append (buildReq) 
                continue 
match = _filterBuildReqsByFlavor (flavor, versionMatches) 
        ...

    
    

    Fix the buggy line: raise RecipeDependencyError (_filterBuildReqsByVersionStr)
assistant
#Here is Python program to find ('@') == (- 1)) : 
.

raise RecipeDependencyError (err)