Try to validate a single attribute for an element basically
          it does the following checks as described by the XML-1.0
          recommendation: - [ VC: Attribute Value Type ] - [ VC:
          Fixed Attribute Default ] - [ VC: Entity Name ] - [ VC:
          Name Token ] - [ VC: ID ] - [ VC: IDREF ] - [ VC: Entity
          Name ] - [ VC: Notation Attributes ]  The ID/IDREF
           uniqueness and matching are done separately

def validateOneAttribute(self, doc, elem, attr, value):
        """Try to validate a single attribute for an element basically
          it does the following checks as described by the XML-1.0
          recommendation: - [ VC: Attribute Value Type ] - [ VC:
          Fixed Attribute Default ] - [ VC: Entity Name ] - [ VC:
          Name Token ] - [ VC: ID ] - [ VC: IDREF ] - [ VC: Entity
          Name ] - [ VC: Notation Attributes ]  The ID/IDREF
           uniqueness and matching are done separately """
        if doc is None: doc__o = None
        else: doc__o = doc._o
        if elem is None: elem__o = None
        else: elem__o = elem._o
        if attr is None: attr__o = None
        else: attr__o = attr._o
        ret = libxml2mod.xmlValidateOneAttribute(self._o, doc__o, elem__o, attr__o, value)
        return ret