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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 _validateClasses(classes):
 """ Check to make sure that a glyph is not part of more than one class. If this is found, an ExtractorError is raised. """

    glyphToClass = {}
    for className, glyphList in classes.items():
        for glyphName in glyphList:
            if glyphName not in glyphToClass:
                glyphToClass[glyphName] = set()
            glyphToClass[glyphName].add(className)
    for glyphName, groupList in glyphToClass.items():
        if len(groupList) > 1:
            raise ExtractorError("Kerning classes are in an conflicting state.")