'Visit an assignment which may have a special comment before it.'

def visit_expr_stmt(self, node):

    if (_eq not in node.children):
        return
    pnode = node[0]
    prefix = pnode.get_prefix()
    while (not prefix):
        pnode = pnode.get_prev_leaf()
        if ((not pnode) or (pnode.type not in (token.INDENT, token.DEDENT))):
            break
        prefix = pnode.get_prefix()
    prefix = prefix.decode(self.encoding)
    docstring = prepare_commentdoc(prefix)
    if docstring:
        self.add_docstring(node, docstring)
