'Resolve the pending_xref *node* with the given *typ* and *target*.
This method should return a new node, to replace the xref node,
containing the *contnode* which is the markup content of the
cross-reference.
If no resolution can be found, None can be returned; the xref node will
then given to the \'missing-reference\' event, and if that yields no
resolution, replaced by *contnode*.
The method can also raise :exc:`sphinx.environment.NoUri` to suppress
the \'missing-reference\' event being emitted.'

def resolve_xref(self, env, fromdocname, builder, typ, target, node, contnode):

    pass
