+It checks the validity of a Service Ticket and returns an XML-fragment response via CAS 2.0 protocol.
+
+It has no arguments.
+
+proxy_validate
+-------------------------
+
+It checks the validity of a Proxy Ticket and returns an XML-fragment response via CAS 2.0 protocol.
+
+It has no arguments.
+
+proxy
+-------------------------
+Creates a proxy ticket for a given Proxy Granting Ticket.
+
+It has no arguments.
+
+
+CUSTOM USER ATTRIBUTES FORMAT
+===========================
+
+Custom attribute format style may be changed in project settings with
+CAS_CUSTOM_ATTRIBUTES_FORMAT constant. You can provide your own formatter callback
+or specify existing in this package in `attribute_formatters` module.
+
+Attribute formatter callback takes two arguments:
+
+* `auth_success` - `cas:authenticationSuccess` node. It is `lxml.etree.SubElement`instance;
+* `attrs` - dictionary with user attributes received from callback specified in
+ CAS_CUSTOM_ATTRIBUTES_CALLBACK in project settings.
+
+Example of generated XML below::
+
+ <cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
+ <cas:authenticationSuccess>
+ <cas:user>jsmith</cas:user>
+
+ <!-- extended user attributes wiil be here -->
+
+ <cas:proxyGrantingTicket>PGTIOU-84678-8a9d2sfa23casd</cas:proxyGrantingTicket>
+ </cas:authenticationSuccess>
+ </cas:serviceResponse>
+
+
+* Name-Value style (provided in `cas_provider.attribute_formatters.name_value`)::
+
+ <cas:attribute name='attraStyle' value='Name-Value' />
+ <cas:attribute name='surname' value='Smith' />
+ <cas:attribute name='givenName' value='John' />
+ <cas:attribute name='memberOf' value='CN=Staff,OU=Groups,DC=example,DC=edu' />
+ <cas:attribute name='memberOf' value='CN=Spanish Department,OU=Departments,OU=Groups,DC=example,DC=edu' />
+
+
+* Jasig Style attributes (provided in `cas_provider.attribute_formatters.jasig`)::
+
+ <cas:attributes>
+ <cas:attraStyle>Jasig</cas:attraStyle>
+ <cas:surname>Smith</cas:surname>
+ <cas:givenName>John</cas:givenName>
+ <cas:memberOf>CN=Staff,OU=Groups,DC=example,DC=edu</cas:memberOf>
+ <cas:memberOf>CN=Spanish Department,OU=Departments,OU=Groups,DC=example,DC=edu</cas:memberOf>
+ </cas:attributes>
+