I am trying to compute with SymPy the taylor series of a function which depends on the trigonomertic function **sinc** ([here](http://docs.sympy.org/dev/modules/mpmath/functions/trigonometric.html#sinc-function)), to simplify my problem, we can assume the function I need the Taylor series of is :

```
f(x1, x2) = sinc(x1) * sinc(x2)

```

My problem is that when importing **sympy.mpmath** I often get the error : 

> 
> cannot create mpf from ...
> 
> 
> 

I have tried to use the [taylor-series](http://docs.sympy.org/dev/modules/mpmath/calculus/approximation.html#taylor-series-taylor) approximation or [this other solution](https://stackoverflow.com/questions/22857162/multivariate-taylor-approximation-in-sympy) (number 1.), but they all seem to fail. For example for the later alternative the line : 

```
(sinc(x)*sinc(y)).series(x,0,3).removeO().series(y,0,3).removeO()

```

returns :

> 
> cannot create mpf from x
> 
> 
> 

I also have tried of defining the function as an expression and as a lambda function. But nothing seems to work.

Any help will be much appreciated.