Here's an example DECLARE model in pm4py format for a hypothetical Purchase-to-Pay process:

```
declare_model = {
    'existence': {  # Existence: the activity is executed at least once.
        'place_order': {'support': 1.0, 'confidence': 1.0},
        'create_invoice': {'support': 1.0, 'confidence': 1.0},
        'make_payment': {'support': 1.0, 'confidence': 1.0}
    },
    'absence': {  # Absence: the activity is not executed.
        'place_order': {'support': 1.0, 'confidence': 1.0},  # No need for absence constraint as all activities have existence
        'create_invoice': {'support': 1.0, 'confidence': 1.0},
        'make_payment': {'support': 1.0, 'confidence': 1.0}
    },
    'exactly_one': {  # Exactly 1: the activity is executed exactly one time.
        'place_order': {'support': 1.0, 'confidence': 1.0},
        'create_invoice': {'support': 1.0, 'confidence': 1.0},
        'make_payment': {'support': 1.0, 'confidence': 1.0}
    },
    'init': {  # Initialization: the trace starts with one of the given activities.
        'place_order': {'support': 1.0, 'confidence': 1.0},  # Start with placing an order
        'create_invoice': {'support': 1.0, 'confidence': 1.0},  # or create an invoice
    },
    'responded_existence': {  # Responded existence: given a couple of activities (A, B), if A occurs then B also occurs.
        ('place_order', 'create_invoice'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Create invoice
    },
    'coexistence': {  # Co-Existence: given a couple of activities (A, B), if A occurs then B also occurs.
        ('place_order', 'create_invoice'): {'support': 1.0, 'confidence': 1.0},  # Place order and Create invoice
    },
    'response': {  # Response: given a couple of activities (A, B), if A occurs then B also occurs in the future of the trace.
        ('place_order', 'create_invoice'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Create invoice in the future
    },
    'precedence': {  # Precedence: given a couple of activities (A, B), if B occurs then also A occurs in the past of the trace.
        ('create_invoice', 'place_order'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Place order
    },
    'succession': {  # Succession: given a couple of activities (A, B), both the response and precedence constraints are satisfied.
        ('create_invoice', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Make payment
    },
    'altresponse': {  # Alternate response: given a couple of activities (A, B), if A occurs then B also occurs, and events must alternate without repetitions.
        ('place_order', 'create_invoice'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Create invoice
    },
    'altprecedence': {  # Alternate precedence: given a couple of activities (A, B), if A occurs then B also occurs in the past of the trace, and events must alternate without repetitions.
        ('create_invoice', 'place_order'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Place order
    },
    'altsuccession': {  # Alternate succession: given a couple of activities (A, B), both the response and precedence constraints are satisfied, and events must alternate without repetitions.
        ('create_invoice', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Make payment
    },
    'chainresponse': {  # Chain response: given a couple of activities (A, B), if A occurs then B also occurs in the future of the trace.
        ('place_order', 'create_invoice'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Create invoice in the future
    },
    'chainprecedence': {  # Chain precedence: given a couple of activities (A, B), if B occurs then also A occurs in the past of the trace.
        ('create_invoice', 'place_order'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Place order
    },
    'chainsuccession': {  # Chain succession: given a couple of activities (A, B), both the response and precedence constraints are satisfied.
        ('create_invoice', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Create invoice -> Make payment
    },
    'noncoexistence': {  # Non Co-Existence: given a couple of activities (A, B), if A occurs then B should not occur.
        ('place_order', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Make payment
    },
    'nonsuccession': {  # Non Succession: given a couple of activities (A, B), B should not follow A.
        ('place_order', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Make payment
    },
    'nonchainsuccession': {  # Non Chain succession: given a couple of activities (A, B), B should not follow A.
        ('place_order', 'make_payment'): {'support': 1.0, 'confidence': 1.0},  # Place order -> Make payment
    }
}

print(declare_model)
```

This DECLARE model captures the typical workflow for a Purchase-to-Pay process, where an organization places an order, creates an invoice, and makes a payment. It defines constraints for the existence of each activity, co-existence and succession between activities, as well as non-co-existence and non-succession constraints to ensure that certain events do not occur simultaneously or in sequence.

Please note that this is just one possible way to model a Purchase-to-Pay process using DECLARE, and actual requirements may vary depending on the specific business needs and process variations.