<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_tool_filepath(self, tool_alias):
 """Given a visible tool alias, return the full path to the executable. Args: tool_alias (str):
 Tool alias to search for. Returns: (str):
 Filepath of executable, or None if the tool is not in the suite. May also return None because this suite has not been saved to disk, so a filepath hasn't yet been established. """

        tools_dict = self.get_tools()
        if tool_alias in tools_dict:
            if self.tools_path is None:
                return None
            else:
                return os.path.join(self.tools_path, tool_alias)
        else:
            return None