'Gets a new grouped symbol whose output contains
inputs to output nodes of the original symbol.
Example usage:
>>> x = mx.sym.Variable(\'x\')
>>> y = mx.sym.Variable(\'y\')
>>> z = mx.sym.Variable(\'z\')
>>> a = y+z
>>> b = x+a
>>> b.get_children()
<Symbol Grouped>
>>> b.get_children().list_outputs()
[\'x\', \'_plus10_output\']
>>> b.get_children().get_children().list_outputs()
[\'y\', \'z\']
Returns
sgroup : Symbol or None
The children of the head node. If the symbol has no
inputs then ``None`` will be returned.'

def get_children(self):

    handle = SymbolHandle()
    check_call(_LIB.MXSymbolGetChildren(self.handle, ctypes.byref(handle)))
    ret = Symbol(handle=handle)
    if (len(ret.list_outputs()) == 0):
        return None
    return ret
