docs: def get_variables(self):
          """
          Returns list of variables of the network
  
          Example
          -------------
          >>> from pgmpy.readwrite import BIFReader
          >>> reader = BIFReader("bif_test.bif")
          >>> reader.get_variables()
          ['light-on','bowel_problem','dog-out','hear-bark','family-out']
          """
          variable_names = []
          for block in self.variable_block():
              name = self.name_expr.searchString(block)[0][0]
              variable_names.append(name)
  
          return variable_names