def lookup_module_function( module_reference, function_name ):
    """
    Acquires a function reference from a module given an function name.

    Takes 2 arguments:

      module_reference - Module whose interface is searched for function_name.
      function_name    - String specifying the function whose handle is sought.

    Returns 1 value:

      function_reference - Reference to the requested function.  None if function_name
                           is not part of module_reference's interface or if there was
                           an error acquiring the reference.
    """

    # get a reference to the function requested.  return None if it isn't part
    # of the module's interface.
    function_reference = getattr( module_reference,
                                  function_name,
                                  None )

    return function_reference