Transform.affine docs says:

    mxx - the X coordinate scaling element of the 3x4 matrix
    mxy - the X coordinate shearing element of the 3x4 matrix
    mxz - the XZ element of the 3x4 matrix

Affine docs says:

mxx
Defines the X coordinate scaling element of the 3x4 matrix.

mxy
Defines the XY coordinate scaling element of the 3x4 matrix.

mxz
Defines the XZ coordinate scaling element of the 3x4 matrix.

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etc