'Returns a copy of this parameter on one context. Must have been
initialized on this context before.
Parameters
ctx : Context
Desired context.
Returns
NDArray on ctx'

def data(self, ctx=None):

    if (ctx is None):
        list_ctx = self.list_ctx()
        if (len(list_ctx) == 1):
            ctx = list_ctx[0]
        else:
            ctx = context.current_context()
    self._check_initialized(ctx)
    return self._data[ctx]
