def attribute(element, attribute, default=None):
attribute_value = element.get(attribute)<EOL>return attribute_value if attribute_value is not None else default<EOL>
Returns the value of an attribute, or a default if it's not defined
:param element: The XML Element object
:type  element: etree._Element

:param attribute: The name of the attribute to evaluate
:type  attribute: basestring

:param default: The default value to return if the attribute is not defined