Document Field instance reuse workaround (#1730)

* Document Field instance reuse workaround

Fixes: #1680

Signed-off-by: LundyBernard <lundy.bernard@gmail.com>

* Update dataframe_models.md

---------

Signed-off-by: LundyBernard <lundy.bernard@gmail.com>
Co-authored-by: Niels Bantilan <niels.bantilan@gmail.com>

docs/source/dataframe_models.md

@@ -107,6 +107,22 @@ class InputSchema(pa.DataFrameModel):
  day: int = pa.Field(ge=0, le=365, coerce=True)
 ```
 
+### Reusing Field objects
+
+To define reuseable `Field` definitions, you need to use `functools.partial`.
+This makes sure that each field attribute is bound to a unique `Field` instance.
+
+```{code-cell} python
+from functools import partial
+from pandera import DataFrameModel, Field
+
+NormalizedField = partial(Field, ge=0, le=1)
+
+class InputSchema(DataFrameModel):
+ xnorm: float = NormalizedField()
+ ynorm: float = NormalizedField()
+```
+
 ## Validate on Initialization
 
 *new in 0.8.0*