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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 generate_format(self):
 """ Means that value have to be in specified format. For example date, email or other. .. code-block:: python {'format': 'email'} Valid value for this definition is user@example.com but not @username """

        with self.l('if isinstance({variable}, str):'):
            format_ = self._definition['format']
            if format_ in self.FORMAT_REGEXS:
                format_regex = self.FORMAT_REGEXS[format_]
                self._generate_format(format_, format_ + '_re_pattern', format_regex)
            # format regex is used only in meta schemas
            elif format_ == 'regex':
                with self.l('try:'):
                    self.l('re.compile({variable})')
                with self.l('except Exception:'):
                    self.l('raise JsonSchemaException("{name} must be a valid regex")')
            else:
                self.l('pass')