code: def add_statements(self, stmts):
          
          for stmt in stmts:
              if not self.statement_exists(stmt):
                  self.statements.append(stmt)
docs: Add INDRA Statements to the assembler's list of statements.
  
          Parameters
          ----------
          stmts : list[indra.statements.Statement]
              A list of :py:class:`indra.statements.Statement`
              to be added to the statement list of the assembler.