delta sometimes appears in 'amount'

[CJBartel]

This occurs 2 times.

This seems irregular, considering for all other 'oxygen_deficiency = True examples, there is no delta in 'amount'

2 examples

Item 441:
data['target']['composition'] = {'(SrCoO3-δ)1-x(Sr2Fe3O6.5±δ)x': {'elements': {'Sr': '-x + 1', 'Co': '-x + 1', 'O': '(x - 1)*(δ - 3)'}, 'amount': '1.0'}}

Item 4866:
data['target']['composition'] = {'(YBa2Cu3O7-δ)1-x': {'elements': {'Y': '-x + 1', 'Ba': '-2*x + 2', 'Cu': '-3*x + 3', 'O': '(x - 1)*(δ - 7)'}, 'amount': '1.0'}}