Visit the whole module and add all import at the top level.

        >> import numpy.linalg

        Becomes

        >> import numpy

def visit_Module(self, node):
        """
        Visit the whole module and add all import at the top level.

        >> import numpy.linalg

        Becomes

        >> import numpy

        """
        node.body = [k for k in (self.visit(n) for n in node.body) if k]
        imports = [ast.Import([ast.alias(i, mangle(i))]) for i in self.imports]
        node.body = imports + node.body
        ast.fix_missing_locations(node)
        return node