<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def list_filepaths(self, wildcard=None):
 """ Return the list of absolute filepaths in the directory. Args: wildcard: String of tokens separated by "|". Each token represents a pattern. If wildcard is not None, we return only those files that match the given shell pattern (uses fnmatch). Example: wildcard="*.nc|*.pdf" selects only those files that end with .nc or .pdf """

        # Select the files in the directory.
        fnames = [f for f in os.listdir(self.path)]
        filepaths = filter(os.path.isfile, [os.path.join(self.path, f) for f in fnames])

        # Filter using the shell patterns.
        if wildcard is not None:
            filepaths = WildCard(wildcard).filter(filepaths)

        return filepaths