'Convert ``elem`` into the internal represantition.
Mostly called implicitly.
>>> from sympy.abc import x
>>> from sympy import QQ
>>> M = QQ.old_poly_ring(x).free_module(2).submodule([1, x])
>>> M.convert([2, 2*x])
[2, 2*x]'

def convert(self, elem, M=None):

    if (isinstance(elem, self.container.dtype) and (elem.module is self)):
        return elem
    r = copy(self.container.convert(elem, M))
    r.module = self
    if (not self._contains(r)):
        raise CoercionFailed
    return r
