Indent an XML string

### 2.7.6 Indent an XML string

The xml_print command formats an XML string.

- xml_print takes str, a string, assumed to contain XML.
- xml_print(str) returns a string with the XML code indented for better readability. The default indentation is two spaces.

#### Example

xml_print("<?xml version='1.0'?><r><c1>bla</c1><c2></c2><c3/></r>")

<?xml version='1.0'?> <r> <c1>bla</c1> <c2></c2> <c3/> </r>