code: @Nonnull
    public EChange removeFunctionsWithName (@Nullable final QName aName)
    {
      EChange eChange = EChange.UNCHANGED;
      if (aName != null)
      {
        // Make a copy of the key set to allow for inline modification
        for (final XPathFunctionKey aKey : m_aMap.copyOfKeySet ())
          if (aKey.getFunctionName ().equals (aName))
            eChange = eChange.or (removeFunction (aKey));
      }
      return eChange;
    }
docs: Remove all functions with the same name. This can be helpful when the same
  function is registered for multiple parameters.
  
  @param aName
  The name to be removed. May be <code>null</code>.
  @return {@link EChange#CHANGED} if at least one function was removed.