I'm new at Python and I'm trying to use a XML file. I know how to parse and search information knowing the structure but I don't knows how to search a value without knowing the tag this value is attached to.

for example : 

```
<bookstore>
  <book category="COOKING">
  <title lang="en">Everyday Italian</title>
  <author>TRUE</author>
  <year>2005</year>
  <price>30.00</price>
</book>
  <book category="CHILDREN">
  <title lang="en">Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>
<book category="WEB">
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>TRUE</year>
  <price>39.95</price>
  </book>
<adventure>
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>TRUE</year>
  <price>TRUE</price>
</adventure>
</bookstore>

```

In this example, I would like to find all "TRUE" values an replace this value to "OK". How would you do that ? 

Thank you