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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 check_singlekey(self):

 """Check if the first sub-sequence of the new key sequence is valid."""

        if len(self._qsequences) == 0:
            return True
        else:
            keystr = self._qsequences[0]
            valid_single_keys = (EDITOR_SINGLE_KEYS if
                                 self.context == 'editor' else SINGLE_KEYS)
            if any((m in keystr for m in ('Ctrl', 'Alt', 'Shift', 'Meta'))):
                return True
            else:
                # This means that the the first subsequence is composed of
                # a single key with no modifier.
                valid_single_keys = (EDITOR_SINGLE_KEYS if
                                     self.context == 'editor' else SINGLE_KEYS)
                if any((k == keystr for k in valid_single_keys)):
                    return True
                else:
                    return False