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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_by(self, field, value):
 """ Gets all Users that match the filter. The search is case-insensitive. Args: field: Field name to filter. Accepted values: 'name', 'userName', 'role' value: Value to filter. Returns: list: A list of Users. """

        if field == 'userName' or field == 'name':
            return self._client.get(self.URI + '/' + value)
        elif field == 'role':
            value = value.replace(" ", "%20")
            return self._client.get(self.URI + '/roles/users/' + value)['members']
        else:
            raise HPOneViewException('Only userName, name and role can be queried for this resource.')