this is a python version of hybrid A star algorithm
reference: @mastersthesis{Kurzer1057261, author = {Kurzer, Karl}, institution = {KTH, Integrated Transport Research Lab, ITRL}, pages = {63}, school = {KTH, Integrated Transport Research Lab, ITRL}, title = {Path Planning in Unstructured Environments : A Real-time Hybrid A* Implementation for Fast and Deterministic Path Generation for the KTH Research Concept Vehicle}, series = {TRITA-AVE}, ISSN = {1651-7660}, number = {2016:41}, year = {2016} }