Contains:
    Inner Class: Node(object)
        Contains:
            Field: data                     // data held by the Node
            Field: next                     // next node
            Field: prev                     // previous node
            Method: __init__(self, data, next=None, prev=None)  
                                            // constructor
            Method: __str__(self)           // string representation of Node object
                                            //    requirement: returns string 
                                            //                 representation of data field
            Method: __eq__(self, other)     // checks for equality
                                            //    requirement: compares data field to other
            Method: __ne__(self, other)     //                 checks for inequality
                                            //    requirement: compares data field to other
            Method: update(self, new_data)  // updates data field of this Node
    Field: head                           // leading node
    Field: tail                           // trailing node
    Field: size                           // total count of all nodes
    Method: __init__(self)                // constructor
    Method: __str__(self)                 // string representation of Doubly Linked List
                                          //    requirement: returns string in format
                                          //                 "[a, 2, c]" for a list of
                                          //                 three nodes where 0, 1, 2 have
                                          //                 data values of "a", 2, "c"
    Method: add_head(self, data)          // adds a node containing data to leading end
    Method: add_tail(self, data)          // adds a node containing data to trailing end
    Method: add(self, data)               // adds a node containing data to trailing end
    Method: remove_data(self, data)       // if data is in the list, removes that
                                          //    node and fixes pointers
    Method: remove_position(self, place)  // if the nth node (place) is in this list,
                                          //    removes that node and fixes pointers
                                          //    0-based indexing required.
    Method: query_position(self, place)   // if the nth node (place) is in this list,
                                          //    returns the data in that node
                                          //    0-based indexing required.
    Method: find_data(self, data)         // if the given data is in this list,
                                          //    returns the position in this list.
                                          //    0-based indexing required.
    Method: update_position(self, place, data)
                                          // if the nth node (place) is in this list,
                                          //    updates the data in that node
    Method: len(self)                     // returns thenumber of nodes in this list

 test_node_str()
 test_node_equals()
 test_node_update()
 test_dll_add()
 test_dll_add_head()
 test_ddl_add_tail()
 test_dll_string()
 test_remove_data()
 test_remove_position()
 test_query_position()
 test_find_data()
 test_update_position()
 test_len()

 pytest [path/to/test]/[test_name].py -k ‘[method_name]’
 e.x.
 pytest ./tests/dll_tests.py -k 'test_node_str'