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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_pval_field(self):
 """Get 'p_uncorrected' or the user-specified field for determining significant results."""

        pval_fld = self.args.pval_field
        # If --pval_field [VAL] was specified
        if pval_fld is not None:
            if pval_fld[:2] != 'p_':
                pval_fld = 'p_' + pval_fld
        # If only one method was used, use that instead of the uncorrected pvalue
        elif len(self.methods) == 1:
            pval_fld = 'p_' + self.methods[0]
        # Use 'uncorrected pvalue' if there are many methods & none chosen using --pval_field
        else:
            pval_fld = 'p_uncorrected'
        if self.results_all:
            assert hasattr(next(iter(self.results_all)), pval_fld), \
                'NO PVAL({P}). EXPECTED ONE OF: {E}'.format(
                    P=self.args.pval_field,
                    E=" ".join([k for k in dir(next(iter(self.results_all))) if k[:2] == 'p_']))
        return pval_fld