code: def get_statements(self):
          
          stmt_lists = [v for k, v in self.stmts.items()]
          stmts = []
          for s in stmt_lists:
              stmts += s
          return stmts
docs: Return a list of all Statements in a single list.
  
          Returns
          -------
          stmts : list[indra.statements.Statement]
              A list of all the INDRA Statements in the model.